sex-segregated public bathrooms existed since at least the 1880s, originally labelled in writing. The stick-figure pictograms were popularized with their introduction by British Rail in the 1960s. The genius behind the stick figure toilet signs, BBC Future (2014).
"One of the best early examples of intuitive global signs for public lavatories was that created for British Rail in the mid-1960s. [...] In the 1970s, the British example was developed on a more comprehensive basis in the United States. In 1974, the US Department of Transportation commissioned the American Institute of Graphic Arts to create a set of pictograms to be used throughout public transport networks whether road, rail, air or sea."
"In Poland, meanwhile, you can come across lavatories indicating “gents” with a triangle and “ladies” with a circle, while in Lithuania men are represented by an inverted pyramid and women by a pyramid standing the right way up."
“Symbolism”. LGBTQA+ WebCenter. Eastern Illinois University. 31 December 2015閲覧。 “Double interlocking female symbols are often been used [sic] to symbolize lesbianism, but some feminists have instead used the double female symbols to represent sisterhood among women and three interlocking female symbols to denote lesbianism. In the 1970’s, some lesbian feminists used three interlocking female symbols to represent their rejection of male standards of monogamy.”
jstor.org
Stearn, William T. (May 1962). “The Origin of the Male and Female Symbols of Biology”. Taxon11 (4): 109–113. doi:10.2307/1217734. JSTOR1217734.
