I'm not an Azed 'regular', NaC, but I could see the OP was trying to work out where/how the (mut)TON came in. I just saw 'surfeit = Glut' and took it from there. I hope it is right! :))
The indication is that ton is half of mutton coming after glu (t). Now looked up mutton and see the em/en connection so have as usual learnt something new;