Pin up Girls

A pin-up girl is a woman whose physical attractiveness would entice one to place a picture of her on a wall. The term was first attested to in English in 1941; however the practice is documented back at least to the 1890s. The “pin up” images could be cut out of magazines or newspapers, or be from postcard or chromo-lithographs, and so on. Such photos often appear on calendars, which are meant to be pinned up anyway. Later, posters of “pin-up girls” were mass-produced.

Excerpt from: http://www.arthistoryarchive.com/arthistory/pinupart/