in France and U.S., "1,000 to the hundredth power," 1846, from centi- "one hundred" (in reference to the 100 groups of three zeroes it has beyond the first group of three zeroes) + ending from million, etc. Compare French centillion (by 1841). Generally used indefinitely for "a very large number." Related: Centillionth.
mid-15c., "ten parts" (of anything; originally in reference to the divisions of Livy's history), from Old French décade (14c.), from Late Latin decadem (nominative decas), from Greek dekas (genitive dekados) "group of ten," from deka "ten" (from PIE root *dekm- "ten"). Meaning "period of ten consecutive years" is 1590s in English. Related: Decadal; decadary.
Mafia code of obedience to the leader and silence about the organization and its business, 1909, from Italian omertà, a dialectal form of umilta "humility," in reference to submission of individuals to the group interest, from Latin humilitas "lowness, small stature; insignificance; baseness, littleness of mind," in Church Latin "meekness," from humilis "lowly, humble," literally "on the ground," from humus "earth," from PIE root *dhghem- "earth."