Pineapple isn't related to pine or apple. English muffins don't come from England and the French didn't invent french fries. Sweetmeats are candies. Swetbreads, which are neither sweet nor bread, are meat. Quicksand is often slow.
Boxing rings are square.
Guinea pigs are not from Guinea, and they're not pigs. Although writers write, fingers don't fing, grocers don't groce, and hammers don't ham. We have two teeth, but the plural of booth isn't beeth. One goose, two geese. In the present tense, teachers teach and preacher preach.