"short, thick stick used as a weapon," Old English cycgel "club with rounded head;" perhaps from PIE *geu- "to curve, bend."
cudgel (v.)
"to strike or beat with a cudgel," 1590s, from cudgel (n.). Related: Cudgeled; cudgeling.
cuckoo
cucumber
cud
cuddle
cuddly
cudgel
cue
cuff
Cuffy
cui bono
cuirass