"device by means of which a catch or spring is released and a mechanism set in action," 1650s, earlier tricker (1620s), from Dutch trekker "trigger," from trekken "to pull" (see trek). Tricker was the usual form in English until c. 1750. Trigger-finger "forefinger as used to pull the trigger of a gun" is attested by 1814. Trigger-happy "ready to shoot (or otherwise react violently) on the slightest provocation" is attested from 1942.
Track record (1955) is a figurative use from racing, "performance history" of an individual car, runner, horse, etc. (1907, but the phrase was more common in sense "fastest speed recorded at a particular track"). To make tracks "move quickly" is American English colloquial first recorded 1835; to cover (one's) tracks in the figurative sense first attested 1898; to keep track of something is attested from 1883. American English wrong side of the tracks "bad part of town" is by 1901. Track lighting attested from 1970.
c. 1200, "a tossing, rolling;" mid-13c., "an act of walking, a going on foot;" late 14c., "a stroll," also "a path, a walkway;" from walk (v.). The meaning "broad path in a garden" is from 1530s. Meaning "particular manner of walking" is from 1650s. Meaning "manner of action, way of living" is from 1580s; hence walk of life (1733). Meaning "range or sphere of activity" is from 1759. Sports sense of "base on balls" is recorded from 1905; to win in a walk (1854) is from horse racing (see walk-over). As a type of sponsored group trek as a fund-raising event, by 1971 (walk-a-thon is from 1963).