You won't be too surprised by some of them actually: bog, bourbon, druid, shamrock, corgi, whiskey, crumpet. Others you'll find here have more circuitous routes where maybe just one phoneme stems from old Gaelic or something, into Latin, into Germanic or Old French, then into Old English, like "ambassador." I'm guessing most of the really Celtic words are used in the British Isles more than elsewhere in the English-speaking world.