It’s the Gaelic spelling of “jail”. It hasn’t been used in mainstream British English since the 60s, outside of specific place names. Everyone in England says “jail” or “prison” today. It might be a bit different in Ireland.

Interesting! I assumed it was one of these loaned-but-misspelled words from French (geôle, pronounced johl with a soft j). I wonder if there’s a common etymology between the French and Gaelic

I think the PP was mistaken when they attributed it to Gaelic. It does indeed come from an antecedent of geôle; probably the spelling comes from the Norman form whereas the pronunciation comes from more widespread French forms. In any case, it isn't a case of "loaned-but-misspelled"; English got most of these words from times before French had standard spellings or - as in this case - pronunciations. And once they became part of English, they were subject to the future developments of English as English words, no longer French. It's like saying "geôle" is just misspelt Latin "caveola".