Gay nickname, for one whose sex life is so predictable, so narrow in focus, that one can't tell one boyfriend from the next.
Mainly a gay nickname, applied to someone who is fairly tame in their sexual tastes, both in sex and in partners.
No need to know the name, as they blend into being all the same.
Characteristics, attitude, etc. are pretty well standard, no sense of adventure, in other words.
Coined in the 1970's, it refers to how one treats their partners the same, as if they were all photographed copies of each other.
Derived from the popular photocopier of the time, Xerox.