Jasper

Jasper never liked his name and planned to change it someday.

None of your sass, Jasper, or I'll keelhaul you!

The personality of Jasper is familiar to the author, so he works for a month or two and remoulds the play to fit him.

And list'nin to some big out-a-town jasper / Hearin' him tell about horse-race gamblin' / Not a wholesome trottin' race, no!

"I stood there through almost an hour of it before they called Rooster Cogburn to the stand. I had guessed wrong as to which one he was, picking out a younger and slighter man with a badge on his shirt. And I was surprised when an old one-eyed jasper that was built along the lines of Grover Cleveland went up and was sworn."

Standing on the corner like a just-got-in-town jasper

“That jasper,” sniggered Darby, “never pulled out his ‘dummy’ for nothing but pissing, I bet you!”

Her husband is...let me see...oh yes, he's Lord Jasper Jayne. His name sounds like the hero of a servant's novelette, but he doesn't look like that. He looks like a chucker-out in a back-street pub.