"one who flees," late 14c., agent noun from flee (v.).

"grin mockingly," c. 1400, perhaps from Scandinavian (compare dialectal Norwegian flira "giggle, laugh at nothing," dialectal Danish flire "to grin, sneer, titter"). Transitive sense from 1620s. Related: Fleered; fleering; fleeringly. As a noun from c. 1600.