"one easily deceived or led astray by false representations," 1680s, from French dupe "deceived person," from duppe (early 15c.), thieves' jargon, perhaps from phrase de huppe "of the hoopoe," an extravagantly crested and reputedly stupid bird. For names of supposedly stupid birds applied to stupid persons, compare booby, goose (n.), gull (n.2) .
[European crow], Middle English roke, from Old English hroc, from Proto-Germanic *khrokaz (source also of Old Norse hrokr, Middle Dutch roec, Dutch roek, Middle Swedish roka, Old High German hruoh "crow"), probably imitative of its raucous voice. Compare crow (n.), also Gaelic roc "croak," Sanskrit kruc "to cry out." Used as a disparaging term for persons at least since c. 1500, and extended by 1570s to mean "a cheat," especially at cards or dice, also, later "a simpleton, a gull, one liable to be cheated" (1590s). For sense, compare gull (n.2).
late 14c., pijoun, "a dove, a young dove" (early 13c. as a surname), from Old French pijon, pigeon "young dove" (13c.), probably from Vulgar Latin *pibionem, dissimilation from Late Latin pipionem (nominative pipio) "squab, young chirping bird" (3c.), from pipire "to peep, chirp," a word of imitative origin. As an English word it replaced culver (Old English culufre, from Vulgar Latin *columbra, from Latin columbula) and native dove (n.).
The meaning "one easily duped, a simpleton to be swindled" is from 1590s (compare gull (n.2)). Pigeon-hearted (1620s) and pigeon-livered (c. 1600) are "timid, easily frightened." A pigeon-pair (by 1800) are twins of the opposite sex (or family consisting of a boy and a girl only), so called because pigeons lay two eggs, normally hatching a male and a female.
seabird, 1857, short for mollymawk, mallemuck, from Dutch mallemok, from mal "foolish" + mok "gull."