from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Archaic A surprise attack by night.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A nocturnal ambush or surprising act of aggression.
Probably from obsolete Spanish encamisado, shirted, surprise attack, from camisa, shirt (so called because the attackers wore white shirts over their armor for identification), from Late Latin camisia, camīsa; see chemise.(American Heritage® Dictionary of the English Language, Fourth Edition)
Spanish encamisado, shirted (Wiktionary)