I never named mine, not really. I just refer to each of them as he/him.
Well, I guess they have sort of nicknames to tell them apart.
Old Roomba or First Roomba or original
Upstairs Rydis or Old Rydis
Downstairs Rydis or New Rydis
Scooba (only needed one)
and now the Braava
So more like designations than names.
By the way all of these work, mostly. My Original needs a new wheel and my Sage needs a new battery. The others are running.