Quiz: Remember the definition of mal de mer?
"to cheat, swindle," 1806, from dialectal duddle, diddle "to totter" (1630s). Meaning "waste time" is recorded from 1825. Meaning "to have sex with" is from 1879; that of "to masturbate" (especially of women) is from 1950s. More or less unrelated meanings that have gathered around a suggestive sound. Related: Diddled; diddling.
A child molester; short eyes (1980s+ Prison)
[cheating sense said to be fr Jeremy Diddler, a character in the 1803 novel Raising the Wind, by James Kenney]