Gandharvas, in the Puranas and Hindu tradition, are divine, celestial beings renowned as expert musicians, singers, and warriors who dwell in the court of Indra or in the sky.
Bhagavata Purana says
After the dissolution of each and every Manu, the next Manu comes in order, along with his descendants, who rule over the different planets; but the seven famous sages, and demigods like Indra and their followers, such as the Gandharvas, all appear simultaneously with Manu.
Rig veda mentions the following words which have, perhaps, the dhatu - gandh (गन्ध्) as origin. However, they are no longer in use in the present days, with their original meanings.
gandharva - गन्धर्व
sugandhim - सुगन्धिं
gandhārīṇām - गन्धारीणाम्
a) Gandharva is the SUPREME BEING or BRAHMAN.
ऊर्ध्वो गन्धर्वो अधि नाके अस्थाद्विश्वा रूपा प्रतिचक्षाणो अस्य । भानुः शुक्रेण शोचिषा व्यद्यौत्प्रारूरुचद्रोदसी मातरा शुचिः ॥
ūrdhvo gandharvo adhi nāke asthād viśvā rūpā praticakṣāṇo asya | bhānuḥ śukreṇa śociṣā vy adyaut prārūrucad rodasī mātarā śuciḥ ||
English translation:
The Gandharva has stood erect upon the vault, gazing upon all his forms. Radiance has flashed forth with blazing blaze; the blazing one has made the two world-halves, the mothers, shine forth.
b) sugandhim - good light/ILLUMINATION
त्र्यम्बकं यजामहे सुगन्धिं पुष्टिवर्धनम् । उर्वारुकमिव बन्धनान्मृत्योर्मुक्षीय मामृतात् ॥
tryambakaṃ yajāmahe sugandhim puṣṭivardhanam | urvārukam iva bandhanān mṛtyor mukṣīya māmṛtāt ||
English translation:
May we adore/meditate the ONE with 3 mothers (tryambakaṃ - त्र्यम्बकं), whose DIVINE ILLUMINATION (sugandhim - सुगन्धिं) pervades everywhere and who strengthens our meditation/prayers (puṣṭivardhanam - पुष्टिवर्धनम् ). Like a cucumber from its stem, (might I) be freed (mukṣīya - मुक्षीय) from death, not from deathlessness.
c) gandhārīṇām - of many DIVINE ILLUMINATIONS
उपोप मे परा मृश मा मे दभ्राणि मन्यथाः । सर्वाहमस्मि रोमशा गन्धारीणामिवाविका ॥
upopa me parā mṛśa mā me dabhrāṇi manyathāḥ | sarvāham asmi romaśā gandhārīṇām ivāvikā ||
English translation:
Come close and closer to me and merge with me (in meditation). Do not think about the little disturbances that you encounter in meditation. You will feel entirely protective of my little ILLUMINATIONS (gandhārīṇām) like a fleece in winter cold.
Hence, the original meaning of the dhatu gandh (गन्ध्) might be light or illumination.
gandharva - gandh + arva
arva indicates running or horse
Hence, gandharva as per Rig Veda indicates an Illumination that spread all over - BRAHMAN
