日本語の「毘沙門天（びしゃもんてん）」は、
サンスクリット語の「ヴァイシュラヴァナ（वैश्रवणः [vaiśravaṇaḥ ]）」から来ています。
ヴァイシュラヴァナとは、お金を司る神様「クベーラ（कुबेरः [kuberaḥ]）」の別名で、
「賢者（リシ）ヴィシュラヴァスの息子」という意味です。
実質的なご利益を期待して、お金を司る神様のクベーラはインド全国で良く知られています。
神様といっても、「ヤクシャ（यक्षः [yakṣaḥ]）」（日本語では夜叉）というステータスで、
デーヴァよりは低いステータスですが、
ヤクシャの王様で、ヴェーダのマントラにも登場ます。
クベーラを讃えるこのマントラは有名なマントラで、
北インドでも南インドでも、テンプルで一般的にチャンティングされています。
https://youtu.be/IRCISc-Vt0E?t=6m10s
https://youtu.be/ZCWj4u9lLfk?t=3m36s
「クベーラーヤ ヴァイシュラヴァナーヤ マハーラージャーヤ ナマハ（クベーラに、ヴァイシュラヴァナに、大いなる王に、尊敬を示します）」という部分は多くの敬虔なイヒンドゥー教徒によく知られています。
https://youtu.be/IRCISc-Vt0E?t=6m10s
https://youtu.be/ZCWj4u9lLfk?t=3m36s
「クベーラーヤ ヴァイシュラヴァナーヤ マハーラージャーヤ ナマハ（クベーラに、ヴァイシュラヴァナに、大いなる王に、尊敬を示します）」という部分は多くの敬虔なイヒンドゥー教徒によく知られています。
クベーラの風貌
ヒンドゥー寺院の中に小さく祀られていたり、ラクシュミーの横に小さく描かれていることが多いです。
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| あらゆる富を司る女神ラクシュミーと一緒に描かれることが多い。横にいるのは妻のリッディ（成功）。 |
クベーラの風貌は、背が小さくて、お腹が出ていて、
金貨の詰まった壺を抱いている、という姿で描写されるのが一般的です。
ラーマーヤナとマハーバーラタにも登場しますが、
原典の中から私が探した限りでは、彼の風貌を描写する部分は見つかりませんでした。
プラーナという、神話を集めた文献にはいろいろ書かれているようです。
１８あるプラーナの中の、ヴァーユ・プラーナでは、
クベーラは、三本の足、八本の歯を持ち、斜視であると伝えられています。（カルパドゥルマより）
その他の詳細は、最後の部分に、プラーナ辞典のエントリー（英文）を載せておきました。
クベーラの出生
一般に良く知られている部分だけを要約しますね。プラスッティヤの息子ヴィシュラヴァスは、
カイカシーとイダヴィダーという名の二人の妻を娶る。
長い間子宝に恵まれなかったのでブランマージーに願掛けをしながら苦行をした結果、
カイカシーはラーヴァナ、クンバカルナ、ヴィビーシャナを授かり、
イダヴィダーはクベーラを授かる。
クベーラはブランマージーに願掛けをした苦行により、
ランカー（現在のスリランカ）の王となるが、
後に異母兄弟であるラーヴァナに追い出され、
宝のひとつであるプシュパカ・ヴィマーナ（直訳すると花の乗り物。乗客の数によって自在に伸び縮みする空飛ぶ絨毯）も略奪される。
詳しくは最後の引用を参照してください。
クベーラの名前の意味
私がよく使う、カルパドゥルマという梵語→梵語辞書によると、こじつけっぽいですが、
１．覆い隠す者 kub（隠す）+ era（者）
２．醜い身体を持つ者 ku (kutsita醜い) + vera (体)
という派生になっております。
参考：
カルパドゥルマ
कुबेर/ कुबे(वे)रः कुबे(वे)रः, पुं, (कुम्बतीति . कुब इ कि आच्छादने“ कुम्बेर्नलोपश्च” . उणां १ . ६० . इति एरक् .नलोपश्च . यद्वा कुत्सितं वेरं शरीरं यस्य . पिङ्गलनेत्रत्वात्तथात्वम् .) यक्षराजः . इति सिद्धान्त-कौमुद्यामुणादिवृत्तिः .. (स च विश्रवस ऋषेरिलविलायां जातः . स तु त्रिपात् अष्टदन्तःकेकराक्षश्च . यथा, वायुपुराणे .“ कुत्सायां क्वितिशब्दोऽयं शरीरं वेरमुच्यते .कुवेरः कुशरीरत्वात् नाम्ना तेनैव सोऽङ्कितः” ..तथा काशीखण्डे देवीदत्तशापोक्तौ च .“ कुवेरो भव नाम्ना त्वं मम रूपेर्ष्यया सुत !” ..)
プラーナ辞典
KUBERA. 1) Genealogy. Descended from Viṣṇu thus: Brahmā-- Pulastya--Viśravas--Kubera. 2) Birth. Pulastya Prajāpati wedded Māninī alias Havir- bhū, daughter of sage Tṛṇabindu, and a son called Viśravas was born to them, Viśravas married Ilibilā alias Daivavarṇinī, daughter of Bharadvāja. Rāvaṇa Kumbhakarṇa and Vibhīṣaṇa were the sons of Viśravas by another wife. (Refer to the genealogy of Rāvaṇa). Viśravas was childless for long, and the above mention- ed four sons were the fruits of the boon granted him by Brahmā, whom he pleased by austerities. (For details see under Viśravas, Para 1). 3) Kubera's attainment of eminence. Once during Kṛta- yuga the Devas went to Varuṇa, and after performing a Yajña for Kubera they told him thus: “In future you live in the ocean itself as deva of all rivers, and let the ocean and the rivers obey you. As in the case of the moon you too will experience waxing and waning.” From that day onwards Kubera became the lord of oceans, rivers, streams etc. and all of them together gave him immense wealth. Śiva became a particular friend of Kubera. (Śalya Parva, Chapter 47). 4) Kubera in Laṅkā. Afterwards Kubera performed penance for ten thousand years in water with head submerged, to please Brahmā. Yet, Brahmā did not appear. Then he performed penance standing on one foot in the centre of Pañcāgni. Brahmā appeared and asked him to choose any boon. Kubera requested that he might be made a lokapālaka (protector of the uni- verse) and the custodian of wealth, and Brahmā respon- ded by supplying Kubera the treasures Śaṅkha nidhi and Padmanidhi and also the Puṣpaka Vimāna as vehicle. He was also appointed one of the Aṣṭadikpāla- kas. (Indra, Agni, Yama, Nirṛti, Varuṇa, Vāyu, Kubera and Īśa are the eight protectors of the eight regions). Kubera's city is called Mahodaya. Kubera felt really happy and told his father Viśravas about his new status and dignity. The father also blessed the son. Kubera requested his father to get a city built for him to live in, and his father asked him to settle down in Laṅkā built by Maya on top of the mountain Trikūṭa in the middle of the south sea. From that day onwards Kubera took his abode in Laṅkā. (It was originally built for Indra). 5) Old history of Laṅkā. Once upon a time when Brahmā was repeating the Vedas he felt hungry. He was annoyed that at that untimely hour he should have felt hungry, and from his angry face emerged the Rākṣasa called Heti. From his hunger emerged the Yakṣa called Praheti. The Rākṣasa turned out to be an unrighteous being, and the Yakṣa a righteous person. Heti married Bhayā, daugher of Kāla, and a son Vidyutkeśa was born to them, who wedded Sālakaṭaṅkā, daughter of Sandhyā. To them were born a child, whom they forsook in the valley of mountain Manthara and went their own. way. Śiva and Pārvatī came that way just then, saw the forsaken child and blessed it. At once the child became a youth. Śiva named him Sukeśa, and he married Devavatī, the daughter of a Gandharva called Maṇimaya. To them were born three sons called Mālyavān, Sumālī. and Mālī. Thanks to the blessings of Śiva all of them became youths as soon as they were born. By means of penances they secured from Brahmā the boon to conquer the three worlds. They then returned to their father. They did not relish the advice of their father to lead a righteous life. They went round the three worlds harassing people. Maya built for them the city called Laṅkā on the top of the Mountain Trikūṭa. There is a story about the origin of Trikūṭa. Once a controversy arose between Vāsuki and Vāyubhagavān as to who was the greater of the two. To prove that he was greater than Vāyu, Vāsuki enveloped with his body mountain Mahāmeru so that Vāyu (wind) could not enter it, and Vāyu tried to blow off the mountain with the result that a dust storm concealed the whole world from view. The Devas took refuge in Viṣṇu, who paci- fied Vāsuki, and he then unwound one coil round the mountain. Vāyu took advantage of the opportunity and swept off one peak of the mountain to the South into the sea, and that peak is Trikūṭa. Mālyavān, Sumālī and Mālī settled down in Laṅkā, and they married Sundarī, Ketumatī and Vasudhā, the three daughters of Narmadā, a Gandharva woman. Seven sons called Vajramuṣṭi, Virūpākṣa, Durmukha, Supta- ghna Yajñakośa, Matta and Unmatta and a daughter called Nalā were born to Mālyavān and Sundarī. Ten sons called Prahasta, Akampa, Vikaṭa, Kālakāmukha, Dhūmrākṣa, Daṇḍa, Supārśva, Saṁhrāda, Prakvāta and Bhāsakarṇa and four daughters called Vekā, Puṣ- potkaṭā, Kaikasī and Kumbhīnasī were born to Sumālī and Ketumatī. Four sons called Anala, Anila, Aha and Sampāti (these four were the ministers of Vibhīṣaṇa) were born to Mālī and Vasudhā. When the harassments of the Rākṣasas became unbear- able the Devas sought protection from Śiva, and Indra detailed to him about the unrighteous actions of Mālya- vān, Sumālī and Mālī. Śiva directed the Devas to Viṣṇu, who set out, to fight against the Rākṣasas. Mālī cut at Garuḍa, and Viṣṇu killed him (Mālī) with his Sudarśana Cakra. The other Rākṣasas retreated to Laṅkā. As their presence in Laṅkā was dan- gerous to the Devas, Viṣṇu directed the Sudarśana Cakra to go to Laṅkā every day and kill the Rākṣasas in groups. The Cakra began its work, and the remaining Rākṣasas escaped to Pātāla. Laṅkā became thus deserted and Kubera took his abode there. The Yakṣas, born from the hunger of Brahmā roamed about without a leader and ultimately settled down in Laṅkā under the leader- ship of Kubera. (Uttara Rāmāyaṇa). 6) Kubera left Laṅkā. The other sons of Viśravas like Rāvaṇa returned with boons from Brahmā for the con- quest of the earth, and the first thing Rāvaṇa did was to drive away his brother Kubera from Laṅkā. He also took by force the Puṣpaka Vimāna of Kubera, who cursed Rāvaṇa thus: “This will never be your vehicle, but will become that of his, who kills you.” Kubera, with the Yakṣas, Kinnaras etc. went north and settled on mount Gandhamādana. (Vana Parva, Chap- ter 275). 7) Kubera's sabhā. The assembly hall of Kubera is 100 yojanas in length and 100 yojanas wide. High walls surround the city. In the centre of the city is a beautiful mansion studded with gems where Kubera sits surrounded by thousands of women. Māruta Deva carrying fragrance from Kalpavṛkṣa worships him. Gandharva and Apsarā women entertain Kubera with music. Miśrakeśī, Ram- bhā, Menakā, Urvaśī, Citrasenā, Śucismitā, Ghṛtācī, Puñjikasthalā, Viśvācī, Sahajanyā, Pramlocā, Vargā, Saurabheyī, Samīcī, Budbudā, and Latā are the chief among them. Maṇibhadra (Māṇibhadra), Dhanada, Āśveta, Bhadra, Guhyaka, Kaśeraka, Gaṇḍakaṇḍu, Pradyota, Mahābala, Ka, Tumburu, Piśāca, Gajakarṇa, Viśāla, Varāhakarṇa, Tāmroṣṭha, Halakakṣa, Halodaka Haṁsacūḍa, Śaṅkhāvarta, Hemanetra, Vibhīṣaṇa, Puṣpānana, Piṅgalaka, Śoṇitoda, Pravālaka, Vṛkṣabāṣ- paniketa, Cīravāsas and Nalakūbara are the chief members in the court of Kubera. Śiva, a good friend of Kubera, very often visits him. Gandharvas and sages like Viśvāvasu, Hāhā, Hūhū, Parvata, Tumburu and Śailūṣa live in Kubera's assembly. Nārada told Dharma- putra that the Kuberasabhā was thus always sweet and pleasant. (Sabhā Parva, Chapter 10). 8) Fight between Kubera and Rāvaṇa. Kubera got secret information that the Devas and the brahmins had decid- ed jointly to complain to Mahāviṣṇu about their unbearable harassment by Rāvaṇa. He sent a messen- ger to his brother Rāvaṇa warning him to lead a more righteous life. Rāvaṇa got so much enraged at the advice of his brother that he cut the messenger into pieces and served as food to the Rākṣasas. Rāvaṇa mobilised his army against Kubera and the Devas, and decided first to attack Kubera. At the head of a huge army led by heroes like Mahodara, Prahasta, Mārīca, Śuka, Sāraṇa, Vajradaṁṣṭra, Dhūmrākṣa, Virūpākṣa, Yūpākṣa, Mahāpārśva, Matta, Unmatta, Vikaṭa, Suptaghna, Yajñāntaka, Makarākṣa, Kumbha- karṇa, Atikāya and Akṣakumāra, Rāvaṇa marched to Alakāpurī where a fierce battle ensued between Rāva- ṇa's and Kubera's armies. Many Yakṣas were killed by Rāvaṇa's army, and the Yakṣa hero Maṇicara killed a large number of Rākṣasas. As a last resort Rāvaṇa thrashed Maṇicara on the head with a club and this turned the hair on his head to one side. From that day Maṇicara came to be known as Pārśvamauli (head turned to one side). In the fight that followed between Kubera and Rāvaṇa the former fell down unconscious. But, the Yakṣas brought two Vimānas and carried Kubera to the palace. Rāvaṇa plundered Kubera's palace and carried off to Laṅkā a lot of costly gems