tiercel

Etymology

From Middle English tercel, from Old French terçuel, from Late Latin tertiolus, the diminutive of Latin tertius (“third”). Sources disagree whether the connection is that the males of most species of birds of prey favoured in falconry are smaller than the females by about a third, or whether it refers to the supposition that only one egg in three yields a male.

noun

1. (falconry) A male hawk or falcon.
   In this wise, the glossy bright-eyed kestrel, whom tiercels’ training could not reclaim, shook off silver bells, and velvet hood, and broidered jesses; and fled away—to consort, henceforward for evermore, with gleds, and hawks, and such birds of prey as make their nests deep in Bohemian forests, or in the desolate places of the Wilderness that girdles the frontier of the reputable world. 1866, George Alfred Lawrence], “Evasit”, in Sans Merci; or, Kestrels and Falcons, volume III, London: Tinsley Brothers,[…], page 126
   He is a tiercel, lean and long and supple-winged, the first of the year. 1967, J. A. Baker, The Peregrine, page 39