kestrel (n.) Look up kestrel at Dictionary.com
kind of falcon, c.1600, earlier castrell (15c.), probably from Middle French cresserelle, which apparently is related to crecerelle "rattle," from Latin crepitacillium "small rattle," diminutive of crepitaculum "noisy bell, rattle," from crepitare "to crackle, rattle;" possibly from the old belief that their noise frightened away other hawks.