IPA: /ˈskʌl.kæp/
KK: /ˈskʌlˌkæp/
A type of close-fitting cap that is usually worn indoors and does not have a brim.
He wore a skullcap during the ceremony to show respect.
Skullcap is formed from "skull" (from Old English *scealu*, meaning the bony structure of the head) and "cap" (from Latin *cappa*, meaning a covering or hood). The word refers to a cap that covers the skull or head.
Think of the 'skull' as the bony part of your head and 'cap' as something that covers it — a skullcap is a covering for the skull.
No commonly confused words.