Want to move away from 'Rob' anything, as it's not my name. I picked Robtard as it was the nickname of an old co-worker of mine.
Guy's name was Rob; had book-smarts next to none, but he had the common sense and social skills of a sheet of plywood. People would often think he had a mental disorder, guy was just odd. 3-4 women in my office would refer to him as "Robtard." I found it funny, albeit a bit cruel.