Cheeky means rudely bold in a way that makes people smile. The child who answers back and gets away with it.
It is a very British word, and the affection in it is essential: calling somebody cheeky is half a telling-off and half a compliment. A cheeky grin, a cheeky question, a cheeky little monkey. It has recently grown a second use meaning a small indulgence you should not really be having — a cheeky pint, a cheeky takeaway, a cheeky day off. The noun behind it is cheek, as in he had the cheek to ask.
Proto-Indo-European
*ǵyewh₁- — to chew
Proto-Germanic
*kēkǭ
Proto-West Germanic
*kākā
Old English
ċēce
Middle English
cheeke
English
cheek
English, today
cheeky
Built from
From cheek + y. Compare typologically barefaced, bald-faced; sfacciato (< ex- + faciēs); effronté, sfrontato (< ex- + frons), czelny (< czoło). cheek comes from Middle English cheeke, cheke, cheoke, choke, from Old English ċēce, ċēace, ċēoce (“cheek; jaw”), from Proto-West Germanic kākā, keukā (“jaw, cheek”), from Proto-Germanic kēkǭ, keukǭ (“jaw; palate; pharynx”), perhaps from Proto-Indo-European ǵyewh₁- (“to chew”). Cognate with stq Sooke (“cheek”), West Frisian tsjeak (“jaw”), Dutch kaak (“jaw; cheek”), Swedish käke (“jaw; jowl”), Norwegian kjake (“jaw”), Old Norse kók (“mouth; gullet”).
Etymology from Wiktionary, CC BY-SA