-cene

early 15c., "recently made," of foods, etc., "fresh, newly made," from Latin recentem (nominative recens) "lately done or made, of recent origin, new, fresh, young," from re- (see re-) + PIE root *ken- "fresh, new, young" (source also of Greek kainos "new;" Sanskrit kanina- "young;" Old Irish cetu- "first," Breton kent "earlier;" Old Church Slavonic načino "to begin," koni "beginning").

Meaning "of or pertaining to the time just before the present" is by 1620s. Related: Recently; recentness ("state or quality of being recent," 1670s, but OED reports recency (1610s) was "Common in 19th c.").

"the third great geological period," 1841, Cainozoic, from Latinized form of Greek kainos "new, fresh, recent, novel" (see recent) + zōon "animal," but here with a sense of "life" (from PIE root *gwei- "to live"). The era that began with the demise of the dinosaurs and the rise of "recent" species and continues to the present; it also is known as the Tertiary. Compare Paleozoic, Mesozoic.

We observe that Lyell, in his geological works, even the most recent, uses the word Cainozoic instead of Coenozoic or Cenozoic. Why the propounder of the terms Eocene, Miocene, etc., should thus spell the word is incomprehensible. If he is right in it, then to be consistent he ought to say Eocain, Miocain, Pliocain, Post-pliocain; for all have the same root καινός. [American Journal of Sciences and Arts, 1873]