Etymologie [ 'kes-tr&l ] (noun.) 15th century. From Middle English castrel (“staniel, bird of prey”), from Middle French cresserelle, crecerelle (“bird of prey”), derivative of crecelle (“rattle, wooden reel”), of obscure origin. Derivation from the assumed Vulgar Latin *crepicella, *crepitacillum, a diminutive of crepitāculum, from crepitāre (“to crackle”) is difficult to explain from a morphological point of view. Instead, possibly from a root *krek-, *krak- (“to crack, rattle, creak, emit a bird cry”), of Germanic origin, from Middle Dutch crāken (“to creak, crack”), from Old Dutch *krakōn (“to crack, creak, emit a cry”), from Proto-Germanic *krakōjanan (“to emit a cry, shout”), from Proto-Indo-European *gArg- (“to shout”). Cognate with Old High German krahhōn (“to make a sound, crash”), Old English cracian (“to resound”), Middle French craquer (used of birds, “to emit a repeated cry”). More at creak, crack.