cockneyyoudaoicibaDictYouDict[cockney 词源字典]
cockney: [14] Etymologically, a cockney is a ‘cock’s egg’ (it comes from cokene, the old genitive plural of cock, and ey, the Middle English word for ‘egg’). This was a medieval term for a small or misshapen egg, the ‘runt’ of the clutch, supposedly laid by a cock, and it came to be applied (probably egged on by Middle English cocker ‘pamper’) to a ‘pampered child’ or ‘mother’s boy’.

In the 16th century we find that it has passed on to ‘town dweller’ (the notion being that people who lived in towns were soft and effete compared with countrymen), and by around 1600 it had started to mean more specifically ‘someone born in the city of London’. The popular definition ‘someone born within the sound of Bow bells’ is first reported by the lexicographer John Minsheu in 1617.
=> cock, egg[cockney etymology, cockney origin, 英语词源]
cockney (n.)youdaoicibaDictYouDict
c. 1600, usually said to be from rare Middle English cokenei, cokeney "spoiled child, milksop" (late 14c.), originally cokene-ey "cock's egg" (mid-14c.). Most likely disentangling of the etymology is to start from Old English cocena "cock's egg" -- genitive plural of coc "cock" + æg "egg" -- medieval term for "runt of a clutch," extended derisively c. 1520s to "town dweller," gradually narrowing thereafter to residents of a particular neighborhood in the East End of London. Liberman, however, disagrees:
[I]n all likelihood, not the etymon of ME cokeney 'milksop, simpleton; effeminate man; Londoner,' which is rather a reshaping of [Old French] acoquiné 'spoiled' (participle). However, this derivation poses some phonetic problems that have not been resolved.
The accent so called from 1890, but the speech peculiarities were noted from 17c. As an adjective in this sense, from 1630s.