Came across this parody of 'The High-Mettled Racer' aka 'The Race Horse' in a 1798 songster full of sophisticated bawdry. In the song the race horse (P-----O) is a euphemism for penis. What I can't work out is what the P----O is meant to be. Pinto springs to mind as a type of horse but if that is simply the case why bother to omit letters. The word is obviously a late 18th century slang for penis but was Pinto used in that way? Pintle/pizzle was penis but pintle-0 has too many syllables. We are looking for a 2-syllable word as with 'racer'. Any suggestions please?

Oh, and no puns on P&O please:) Well, you can if you can come up with a clever one.