- December
[December 词源字典] - December: [13] December was originally so named by the ancient Romans (Latin December) because it was the tenth month of their calendar (which began with March). The term was derived from Latin decem ‘ten’. It reached English via Old French decembre.
=> decimal, ten[December etymology, December origin, 英语词源] - December (n.)
- c. 1000, from Old French decembre, from Latin December, from decem "ten" (see ten); tenth month of the old Roman calendar, which began with March.
The -ber in four Latin month names is probably from -bris, an adjectival suffix. Tucker thinks that the first five months were named for their positions in the agricultural cycle, and "after the gathering in of the crops, the months were merely numbered."
If the word contains an element related to mensis, we must assume a *decemo-membris (from *-mensris). October must then be by analogy from a false division Sep-tem-ber &c. Perhaps, however, from *de-cem(o)-mr-is, i.e. "forming the tenth part or division," from *mer- ..., while October = *octuo-mr-is. [T.G. Tucker, "Etymological Dictionary of Latin"]
