What is the X in X-mas?
1974, from French rétro (1973), supposedly first used of a revival c.1968 of Eva Peron-inspired fashions and short for rétrograde (see retrograde). There is an isolated use in English from 1768, and the word apparently was used in 19c. French as a term in billiards. As a noun, short for retro-rocket (1948) from 1961.
word-forming element meaning "backwards; behind," from Latin retro (prep.) "backward, back, behind," also of time, "formerly, in past times," probably originally the ablative form of *reteros, based on re- "back" (see re-).
L. retro stands to re- as intro, "in, within"; to in, "in," and as citro, "hither," stands to cis, "on this side." [Klein]Common in combinations in post-classical Latin (the classical equivalent was post-). Active in English as a word-forming element from mid-20c.
Backward; back: retroposition.
Situated behind: retroperitoneum.
Nostalgic; historically resurrectional: I'm going to give them retro names like Madge or Verna or Ralphnoun
A retrospective art exhibit, movie festival, etc: the Bleecker's current Godard retro
[1974+; fr retrospective]