Can anyone tell me what part of the cow is the Boston Butt cut? Yes, I do know that for pork, it's the rear of the shoulder...
Called the "butt" because it's the end that adjoins - butts up against - the rest of the pig. I have never in my life seen or heard this term used for beef. The only odd name I know of for beef shoulder is "shoulder clod", whose exact location I would have to look up on some chart that is in none of my books. If someone is calling a cut of beef "Boston butt" I'd assume it's not just a jocular reference to rump roast... ;-)