Origin and evolution of the pejorative slang

In the mid-17th century, dick became slang for a man as a sexual partner.[5] For example, in the 1665 satireThe English Rogue by Richard Head, a "dick" procured to impregnate a character that is having difficulty conceiving:

The next Dick I pickt up for her was a man of a colour as contrary to the former, as light is to darkness, being swarthy; whose hair was as black as a sloe; middle statur'd, well set, both strong and active, a man so universally tryed, and so fruitfully successful, that there was hardly any female within ten miles gotten with child in hugger-mugger, but he was more than suspected to be Father of all the legitimate. Yet this too, proved an ineffectual Operator.[6]

An 1869 slang dictionary offered definitions of dickincluding "a riding whip" and an abbreviation of dictionary, also noting that in the North Country, it was used as a verb to indicate that a policeman was eyeing the subject.[7] The term came to be associated with the penis through usage by men in the military around the 1880s.[1]

https://en.wikipedia.org/wiki/Dick_(slang)