I did some googling and it turns out "gaol" was indeed the more popular spelling, but only up until 1960 when "jail" took over; numbers: https://books.google.co

I did some googling and it turns out "gaol" was indeed the more popular spelling, but only up until 1960 when "jail" took over; numbers: https://books.google.com/ngrams/graph?content=gaol%2Cjail&year_start=1700&year_end=2019&corpus=29&smoothing=30# https://books.google.com/ngrams/graph?content=gaol%2Cjail&ye...