1769, "thing which blights," agent noun from blight (v.). British colloquial sense of "contemptible person" (often jocular) is recorded from 1896.

1610s, "influence, usually hidden or inconspicuous, that nips, blasts, or destroys plants," a word of obscure origin; according to OED it emerged into literary speech from the talk of gardeners and farmers.

It is perhaps from Old English blæce, blæcðu, a scrofulous skin condition and/or from Old Norse blikna "become pale" (from the group including bleach, bleak, etc.). The word came to be used in a general way of agricultural diseases, with or without suggestion of invisible baleful influence; hence the figurative sense of "anything which withers hopes or prospects or checks prosperity" (1660s). Compare slang blighter. Urban blight "condition of disrepair and poverty in a previously thriving part of a city" is attested by 1935.