Morpheme
Fly
Type
free base
Denotation
winged insect
Etymology
Middle English flye, flie; Old English flȳġe, flēoge
Evidence
alderfly, antifly, barfly, blackfly, blowfly, botfly, butterfly, cranefly, damselfly, dragonfly, eggfly, firefly, flier, flies, fliest, fly, fly, flyer, flyest, flyflap, flyleaf, flyless, flyness, flyproof, flyspeck, flyswatter, gadfly, greenfly, horsefly, housefly, hoverfly, mayfly, sandfly, sawfly, whitefly
Notes
<y> need not toggle (but can) with suffixes, especially in monosyllabic bases ending in <y>
“cool, clever” notion probably from the insect being hard to catch
