Meaning

noun the mathematics of triangles and trigonometric functions

adjective neat and smart in appearance

originFrom Middle English trig, tryg, from Old Norse tryggr (“loyal, faithful, true”), from Proto-Germanic *triwwiz (“loyal, faithful, true”). Cognate with Old English trīewe (“faithful, loyal, true”). More at true.

Etymology from Wiktionary, CC BY-SA 3.0