I read 'gaol' the same way. I assumed it meant a squat medieval stone building with an inches thick oak door and a really tiny window. Not at all like American jails, which of course are cells with floor to ceiling iron bars on one side of the sheriff's office, where he can rest his feet on his desk and keep an eye on the cattle rustlers at the same time.
I don't see the rhyme with "goal." None of the lines have internal rhyme, so the line with both "gaol" and "goal" cannot be expected to suddenly rhyme the two. The end-of-line "gaol" and the end-of-line "goal" have their own nearby rhymes, so I doubt they are intended to rhyme from five lines apart. Also, I was recently reminded of the delightful "connexion." I like that one so much. Also also, DERAIL, woo. We could listen to redcap here and go back to beating up saplings.
