Guru came into English in 1806, first spelled gooroo, from Hindi guru, "teacher, priest," and behind that Sanskrit guru-s, "one to be honoured." The literal meaning of the Sanskrit adjective is "heavy, weighty," from an Indo-European root for heaviness — the same root that gives Latin gravis and therefore English gravity and grave. A guru is, etymologically, a person of weight.
It belongs to the substantial layer of words English took from India: bungalow, jungle, shampoo, pyjamas, loot, thug, veranda. Most kept their Indian meaning; guru did not. The generalised sense of a mentor is from 1940, in H.G. Wells, and the thoroughly secular sense of an expert in some field was applied to Marshall McLuhan in Canadian English around 1966, which is roughly where the word has stayed.
guru (n.) "Hindu spiritual teacher or guide," 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." In English the generalized sense of "mentor" is from 1940 (in H.G. Wells); sense of "expert in something" is recorded c. 1966 in Canadian English in reference to Marshall McLuhan. also from 1806
guru came in through Later and wider borrowings, and its spelling follows that family's conventions.
What gives it away on the page
| everyday domestic words from India | Sanskrit-descended languages, via the Raj.shampoo, bungalow, jungle, pyjamas, loot, thug, guru |
Later and wider borrowings in the spelling guide · guess another word's family