'gaol' always throws me for a loop when I'm reading something British. I need to remind myself it's pronounced 'jail'. (A quick google tells me that all the major British newspapers switched over to 'jail' by the 1990's - score one for the good guys!)

I remember reading 'Mutiny on the Bounty' as a child and talking about it with my father and I said something about the 'boatswain', and he (a former naval officer) looked at me like I had two heads. "You mean the [BOSUN]?" "Well, no it says 'boatswain'" "Yes, it's spelled like that, but it's pronounced BOSUN. It's like 'colonel'. Don't think about the letters."