preen (v.)
late 14c., of a person, "to trim, to dress up," probably a variation of Middle English proynen, proinen, of a bird, "trim the feather with the beak;" of a person, "to dress or groom oneself carefully" (see prune (v.)). Middle English prene "to pin, pierce, fasten with a pin" probably influenced the form of this word. It is from Old English preon, a general Germanic word (compare Dutch priemen, Low German prünen, East Frisian prinen).
In English, the use in reference to a bird, "to trim the feathers with the beak," is from late 15c. Because of the late medieval popularity of falconry, bird activities were more closely observed and words for them were more precise in English than today.
Youre hawke proynith and not pikith and she prenyth not bot whan she begynnyth at hir leggys, and fetcheth moystour like oyle at hir taill. ["Book of St. Albans," 1486]
Preening as a present-participle adjective meaning "proud, self-confident" is by 1903.
Others are reading
Dictionary entries near preen
pre-eminent
pre-empt
pre-emption
pre-emptive
pre-emptory
preen
pre-engage
pre-exilic
pre-exist
pre-existence
pre-existing