XXX · symbol, adjective1
1969 (see quotations). Reduplication of X (“an age rating denoting content suitable for adults”), in reference to the X rating introduced by the Motion Picture Association of America on 1 November 1968 for films containing extreme violence, heavily implied (originally softcore) sex and obscene language. Film posters began to include multiple exes (but skipping two) in order to imply even more extreme, hardcore content, particularly in relation to pornography (although many actually contained the same content as X-rated films). Compare XXXX. The original X rating was superseded by NC-17 in 1990; see also R-18.
XXX · symbol, adjective2
Unknown. Possibly from X, a graphic derivative of the skull and crossbones (“indicator of death”). For other possible explanations, see Beer measurement § Saltire marks on WikipediaWikipedia .
XXX · verb3
XXX · symbol4
Perhaps from sXe.
XXX · noun5
From having three X chromosomes (and no Y), or as a clipping of XXX syndrome.
XXX · noun6
Adopted by the International Radiotelegraph Convention in 1927.
Etymology from Wiktionary, CC BY-SA 4.0.