rhamphotheca
/ramfəˈθiːkə/(also ramphotheca) Ornithology
noun
The modified integument, usually horny but in some birds leathery, that covers a bird's jaws and forms the outer layer of the bill.
Origin
Late 19th century; earliest use found in James Graham Cooper (1830–1902). From scientific Latin rhamphotheca from ancient Greek ῥάμϕος beak + θήκη sheath.