a common name for species of flies and similar insects which deposit their eggs on flesh, and taint it, 1720, from fly (n.) + blow (v.1) in an obsolete sense "to deposit eggs, to infect with eggs" (1550s), in reference to insects, "apparently connected with old notions of natural history" [OED]. Hence also flyblown. But blow on or upon meaning "breathe (infectious breath, poison) upon; infect with disease, taint" is by c. 1300, and compare Middle English elf-blown "tainted." Blown also was used in other compounds for "stale from exposure to air," which flows into the senses of "tainted, unsavory; exposed to flies."
updated on October 17, 2022