Came into use in an IRC chat room and quickly took off from there.
<Person A> Hi!
<Person S> DIYM!
<Person A> :|
Contrary to the chat room deffinition, this term was developed by a friend and myself over fifteen years ago, as a way to fuck with a guy at work who we had named "Dicknyamouf". Example. "Hey dicknyamouf, bring me a soda!"