This appears in the German name, Emmerling, and the word probably means the “chirper,” cf. the Ger.
Ah, she is prettier than ever I supposed, and chirper than the sparrow which builds every year a nest in my old apple-tree.
mid-15c. (implied in chirping), echoic, or else a variant of Middle English chirken "to twitter" (late 14c.), from Old English cearcian "to creak, gnash." Related: Chirped. As a noun, attested from 1802.