blightyoudaoicibaDictYouDict[blight 词源字典]
blight: [17] Blight appeared out of the blue in the early 17th century in agricultural and horticultural texts, and its origins are far from clear. It has, however, been speculated that it may be connected with the Old English words blǣce and blǣcthu, both terms for some sort of itchy skin condition such as scabies. These in turn are probably related to Old English blǣcan ‘bleach’, the link being the flaky whiteness of the infected skin.

In Middle English, blǣcthu would have become *bleht, which could plausibly have been the source of blight. A related piece in the jigsaw is blichening ‘blight or rust in corn’, found once in Middle English, which may have come ultimately from Old Norse blikna ‘become pale’.
=> bleach[blight etymology, blight origin, 英语词源]
blight (n.)youdaoicibaDictYouDict
1610s, origin obscure; according to OED it emerged into literary speech from the talk of gardeners and farmers, perhaps ultimately from Old English blæce, blæcðu, a scrofulous skin condition and/or from Old Norse blikna "become pale." Used in a general way of agricultural diseases, sometimes with suggestion of "invisible baleful influence;" hence figurative sense of "anything which withers hopes or prospects or checks prosperity" (1828). Compare slang blighter. Urban blight attested by 1935.
blight (v.)youdaoicibaDictYouDict
"afflict with blight," 1660s (implied in blighted), from blight (n.). Figurative use by 1712. Related: Blighted; blighting.