"native or permanent resident of London," specifically the City of London, more precisely one born or living "within the sound of Bow-Bell" (see Bow bells); c. 1600, usually said to be from Middle English cokenei, cokeney "spoiled child, milksop" (late 14c.), originally cokene-ey "cock's egg" (mid-14c.). The 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" (as though "egg laid by a cock"), 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:
Cockney, 'cock's egg,' a rare and seemingly obsolete word in Middle English, was, in 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 characteristic accent so called from 1890, but the speech peculiarities were noted from 17c. As an adjective in this sense, from 1630s. Related: Cockneydom; Cockneyish.
Proto-Indo-European root meaning "bird." It also might be the source of *wyo, *yyo, Proto-Indo-European words for "egg."
It forms all or part of: auspex; auspices; auspicious; avian; aviary; aviation; aviator; avicide; aviculture; aviform; caviar; cockney; egg (n.); ocarina; oo-; oocyte; oolite; oology; osprey; ostrich; oval; ovary; ovate (adj.); oviform; oviparous; ovoviviparous; ovoid; ovulate; ovulation; ovule; ovum.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit vih, Avestan vish, Latin avis "bird;" Greek aietos "eagle;" Old Church Slavonic aja, Russian jajco, Breton ui, Welsh wy, Greek ōon, Latin ovum, Old Norse egg, Old High German ei, Gothic ada all meaning "egg."
"inhabitant of a city," colloquial shortening of citizen, 1640s; especially "a London cockney," as contrasted to a country man or a gentleman, usually with some measure of opprobrium (Johnson defines it as "A pert low townsman; a pragmatical trader").
derisive word for an old man, 1885, according to OED a variant of obsolete Cockney guiser "mummer, one wearing a mask or costume as part of a performance" (late 15c.; see guise). If so, the original notion was "one who went about in disguise," hence "odd man," hence "old man" (it still commonly is qualified by old).