I hate to step on a cherished memory, but I think it was Sam Sheepdog. It’s not unknown for cartoon characters to go through some minor changes early on, before they settle in to their established forms, so maybe he was Frank at some point. The joke was lampshaded once on Newsradio.
As to The Coyote, there may be some reference to his name that we haven’t discovered yet. Was he ever shown standing by his mailbox waiting for a package from Acme? I know that sort of gag was used in other WB cartoons. What name is in the mailbox?