It’s not Mortimer. I don’t know of any literary character named Mortimer, that appears in any 17th-century literature (although that doesn’t mean there isn’t). I did a cursory perusal of Mortimer Mouse in Wiki, and didn’t see any indication, that his name was based on any literary character from that time.
@RedDeerGuy1‘s answer is conceivably correct, but it’s not the one I’m asking for.
One person here has given the answer I’m looking for.
The third tag in my OP, gives an oblique clue to the answer I seek.