the worm or grub of various insects (especially a fly), formerly supposed to be generated by corruption, late 15c., magat, probably an unexplained variant of Middle English maddok, maðek "earthworm, bedbug, maggot," from Old English maða "maggot, grub," from Proto-Germanic *mathon (source also of Old Norse maðkr, Old Saxon matho, Middle Dutch, Dutch made, Old High German mado, German Made, Gothic maþa "maggot").

Figurative use "whim, fancy, crotchet" is 1620s, from the notion of a maggot in the brain. Hence maggotry "folly, absurdity" (1706).

1660s, "sickly, nauseated" (a sense now obsolete), from Middle English mawke "maggot" (early 15c.; see maggot), but the literal sense of "maggoty" is not found. Figurative meaning "sickeningly sentimental, insipid" is recorded by 1702. Related: Mawkishly; mawkishness.

"lice infestation," 1809, with -osis + Latin pediculus, diminutive of pedis "a louse," said in some sources to be akin to pedere "to break wind" (see petard) on notion of "foul-smelling insect" [Watkins]. But de Vaan traces it to a PIE *pesd- "annoying insect" and compares Avestan pazdu- "beetle, maggot." Pedicule "louse" is attested in Middle English (early 15c.).

"nocturnal lepidopterous insect," Middle English motthe, from Old English moððe (Northumbrian mohðe), a common Germanic word (compare Old Norse motti, Middle Dutch motte, Dutch mot, German Motte "moth"), perhaps related to Old English maða "maggot," or perhaps from the root of midge (q.v.). Until 16c. the word was used mostly of the larva and usually in reference to devouring woolen fabrics (see Matthew vi.20). Words for the adult moth in Middle English included flindre (mid-14c.), which is cognate with Dutch vlinder "butterfly." Moth-eaten is attested from late 14c.