Origin and history of weigh

Middle English weien, from Old English wegan (class V strong verb, past tense wæg, past participle wægon) "find the weight of, measure;" also intransitive, "have weight;" also "lift, carry, support, sustain, bear; move," from Proto-Germanic *wegan (source also of Old Saxon wegan, Old Frisian wega, Dutch wegen "to weigh;" Old Norse vega, Old High German wegan "to move, carry, weigh;" German wiegen "to weigh," bewegen "to move, stir"), from PIE root *wegh- "to go, move, transport in a vehicle."

The prehistoric sense evolution would be from "move" to "lift, raise" to "bear up to determine the weight of." Compare Latin pendere "to weigh; consider," literally "to hang, cause to hang." The sense of "lift, carry" survives in the nautical phrase weigh anchor.

The figurative sense of "consider, ponder, examine" for the purpose of forming an opinion (in reference to words, etc.) is recorded from mid-14c.

To weigh down "overload with too much weight" is by mid-14c., originally figurative (of sin, etc.); physical sense is by 1560s.

To weigh in in the sense of "ascertain one's weight before an athletic contest" is by 1868, originally of jockeys, later prize-fighters; the figurative meaning "bring one's influence to bear, enter forcefully into a discussion" is from 1909.