Roman Catholic skullcap
Skull cap, especially of Roman Catholic clergy; small dome.

ETYM Old Eng. cappe, AS. caeppe, cap, cape, hood, from LL, cappa, capa; perhaps of Iberian origin. Related to Cape, Cope.
1. A top (as for a bottle).
2. Something serving as a cover or protection.
3. Umbrellalike fruiting structure forming the top of a stalked fleshy fungus such as a mushroom; SYN. pileus.