As a deity name
Name 673 of the Gayatri Sahasranāma — Devi Bhagavata Purana, as taught by Sages
As a Hindi name
No reading on this path — this spelling has no entry in our Hindi sources, and no near neighbour is attested there either. We say so rather than invent one.
As a Sanskrit word
Meaning
a red powder usually of the root of wild ginger (coloured with sappan wood and thrown over one another by the Hindūs at the Holī festival; cf. phalgūtsava)
Scripturally attestedWhy this matches what you typed
M1 · same meaning "phalgvai" is the dative of "phalgu" — the same word in a different grammatical case.
Dictionary citations
phalgu mf(ū or u or vī)n. reddish, red, TS.
small, minute, feeble, weak, pithless, unsubstantial, insignificant, worthless, unprofitable, useless, VS. &c. &c.
Caveats
Sources contain errors and engines have limits; every claim above carries its citation so you can verify it. This is guidance about names and their sources — not religious or astrological consultation. How we work · Our sources