Guru
from Hindi and Punjabi, from Sanskrit guru ‘weighty, grave’ (compare with Latin gravis ), hence ‘elder, teacher’.
wiktionary
From Hindi गुरु(guru) / Urdu گرو (guru) / Punjabi ਗੁਰੂ(gurū), from Sanskrit गुरु(guru, “venerable, respectable”), originally "heavy" and in this sense cognate to English grieve. (A traditional etymology based on the Advayataraka Upanishad (line 16) [1] describes the syllables gu as 'darkness' and ru as 'destroyer', thus meaning "one who destroys/dispels darkness"). Doublet of grave, grief, and brute.
etymonline
guru (n.)
1806, gooroo, from Hindi guru "teacher, priest," from Sanskrit guru-s "one to be honored, teacher," from guru- "venerable, worthy of honor," literally "heavy, weighty," from PIE root *gwere- (1) "heavy." Generalized sense of "mentor" is from 1940 (in H.G. Wells); sense of "expert in something" first recorded c. 1966 in Canadian English in reference to Marshall McLuhan.
