Looks almost like a very large Crown of Thorns, but I doubt it. Hard to see if there are any thorns or not, but I've never seen them get a barrel trunk like that. If it is related, it's some euphorbia, which can have a milky sap that can be toxic and irritating. They're common enough though, just don't let pets chew them. That said, I would wait for a more decisive identification

Does it come in lyme?