coop / koōp; koŏp/ • n. a cage or pen for confining poultry: a chicken coop.• v. [tr.] (usu. be cooped up) confine in a small space: being cooped up indoors all day makes him fidgety. ∎  put or keep (a fowl) in a cage or pen.PHRASES: fly the coopsee fly¹ .

coop †basket XIII; cage for poultry XV; place of confinement XVI. — MLG., MDu. kūpe (Du. kuip tub, vat), parallel with OS. kōpa, OHG. kuofa (G. kufe) cask — L. cūpa, also medL. cōpa tun, barrel.
Hence as vb. XVI.