sheldrake (n.)

early 14c., from sheld- "variegated" + drake "male duck." First element cognate with Middle Dutch schillede "separated, variegated," West Flemish schilde, from schillen (Dutch verschillen "to make different"), from Proto-Germanic *skeli-, from PIE root *skel- (1) "to cut." This is the origin considered most likely, though English sheld by itself is a dialect word attested only from c. 1500. OED finds derivation from shield (n.), on resemblance to the patterns on shields, "improbable."