Ok so there is no other pair. but ER is a sort of gender marker.

farmer
cooper
weaver
many verbs become nouns, and tend to connote masculine professions, by adding ER

spin can become spinner, but more often is spinster (ster ending for a term commonly associated with women)

and there also exist blonde and blond (i never can keep track which is supposted to be the feminine form and just use blond.)

my other obsession