IPA: /ˈhʌbˌkæp/
KK: /hʌbˌkæp/
A round cover that fits over the center part of a wheel on a vehicle, often made of metal or plastic.
He polished the hubcap until it shone like new.
Hubcap is formed from "hub" (from Old English "hyb", meaning the central part of a wheel) and "cap" (from Old French "cape", meaning a covering). The word "hubcap" refers to a covering for the central part of a wheel.
Think of the 'hub' as the center of the wheel being covered by a 'cap' — that's what a hubcap does.
No commonly confused words.