What's the "een" in Halloween?
early 14c., from Old French deien (12c., Modern French doyen), from Late Latin decanus "head of a group of 10 monks in a monastery," from earlier secular meaning "commander of 10 soldiers" (which was extended to civil administrators in the late empire), from Greek dekanos, from deka "ten" (see ten). Replaced Old English teoðingealdor. College sense is from 1570s (in Latin from late 13c.).