trig (adj.)

"smart, trim," c. 1200, from Old Norse tryggr "firm, trusty, true," from Proto-Germanic *treuwaz "having or characterized by good faith," from PIE *drew-o-, a suffixed form of the root *deru- "be firm, solid, steadfast." A Scottish and northern word only until 19c. Related: Trigness.

trig (n.)

1895 as a shortening of trigonometry.