Unclear, but likely from Cornishporth(“harbor”) + bugel(“shepherd”), with the latter element either influenced by Englishbeagle or in fact formed from it, with only the first element truly being from Cornish.
In English waters, the porbeagle is considered the premier shark to catch, but in other parts of the world it is considered a nuisance, or at best a poor substitute for its more glamorous relative, the mako.
