From John McWhorter’s delightful Nine Nasty Words, we learn the origin of one of my all-time faves: shit.
English ultimately traces back to a language spoken by people living in what is now Ukraine, who almost certainly used a word skei that meant “cut off” or “slice.” Over the millennia, some of their descendants settled in England, with skei having morphed to scit. But in Old English, its meaning had drifted into a particular kind of cutting off. Likely some people along the way started referring to defecation as going to “cut one off” or the like—the expression to pinch a loaf is unavoidable as a comparison. Sc- soon became sh-, and so just as scip was our ship, scit is, um, yeah.