Lightweight

wiktionary

ref

From light(“not heavy”, adjective) +‎ weight(noun).

etymonline

ref

lightweight (adj.)

also light-weight, 1809, from the noun (1773 in horse-racing, also in pugilism), "man or animal of a certain weight prescribed by rule," from light (adj.1) + weight (n.). Figurative sense of "inconsequential" first attested 1809. The noun sense of "person of little importance or accomplishment" is from 1885.