The fight to cut my dogs nails

Molly

So I have a chihuahua who absolutely hates having his nails cut. He won’t let us do it anymore. He literally sounds like we are killing him and won’t stay still for heck. Hes snapped on us s few times. We’ve also tried calming pills. He is a very skittish dog In general. I found him one day and brought him him but I think he was abused before so I’m thinking that has something do do with it. Does anyone know anything I can do?