Ummm, could go with “35” as in Colt 35 (too small to be a Colt 45) OR (just stop groaning because it will likely get worse) Derringer (same theme as above) OR you could go with Stud-Muffintop (I know, I know, I don’t get paid to do this you know), OR Marshmallow (white and small and smooshy). Wow, I am more tired than even I realized. Now I am on a roll . . .
I have always fancied Walter as a name for a mule, but I would loan it to you under the circumstances (my not having a mule and all). Now I do have a friend whose bull is named Winona (don’t ask). You could go kind of more fake Native American, like Dances with Mice or something.
And my best suggestion of the day is Yardly (he’s hardly a yard). My work here is done.