Origin and history of lightweight

"not heavy, having little actual weight," from Old English leoht (West Saxon), leht (Anglian), "not heavy, light in weight; lightly constructed; easy to do, trifling; quick, agile," also of food, sleep, etc., from Proto-Germanic *lingkhtaz (source also of Old Norse lettr, Swedish lätt, Old Frisian, Middle Dutch licht, German leicht, Gothic leihts), from PIE root *legwh- "not heavy, having little weight." The adverb is Old English leohte, from the adjective.

Meaning "frivolous" is from early 13c.; that of "unchaste" from late 14c., both from the notion of "lacking moral gravity" (compare levity). Of literature from 1590s. Light industry (1919) makes use of relatively lightweight materials. The notion in make light of (1520s) is "unimportance." Alternative spelling lite, the darling of advertisers, is first recorded 1962. Light horse "light armed cavalry" is from 1530s. Light-skirts "woman of easy virtue" is attested from 1590s. Lighter-than-air (adj.) is from 1887.

Middle English weght, from Old English wiht, gewiht "weighing, downward force of a body, physical property of heaviness," from Proto-Germanic *wihti- (source also of Old Norse vætt, Danish vegt, Old Frisian wicht, Middle Dutch gewicht, German Gewicht), from *weg- (see weigh).

By mid-14c. as "piece of metal used on account of its weight" (fishing-weight, etc.). The figurative sense of "burden" is late 14c. In reference to the weights of a clock by 1510s.

By late 14c. as "what one weighs;" to lose weight "get thinner," of persons, is recorded by 1858. Weight Watcher as a trademark name dates from 1960.

The sense of "importance" is by 1520s. To throw (one's) weight around figuratively is by 1922. Weight-training is from 1945. Weight-lifting is from 1885; to lift weights for exercise or muscle development is by 1907; weight-lifter (human) is from 1893.

To pull one's weight was prominent from 1902, a phrase of U.S. President Theodore Roosevelt that caught the attention of political journalists.

The first requisite of a good citizen in this republic of ours is that he shall be able to pull his weight—that he shall not be a mere passenger, but shall do his share in the work that each generation of us finds ready to hand .... [extract from Roosevelt speech at New York Chamber of Commerce, printed in Lincoln (Neb.) Journal Star, Nov., 17, 1902]

The image is from rowing, where it is attested by 1869.

A shade heavy he may be ; but he pulls his weight many times over. So tremendous, indeed, is his muscle, that, if he were to lash out, he would pull the University eight right under water (etc.) [political humor masked as an account of a rowing race, Cheshire Observer, March 20, 1869]