Leather straps or bits of bootlace called "Lallygags" were used in Cambridgeshire up until about WW2 to stop mice running up the trouser legs when working on the (corn) stacks. I've never seen a rabbit going up anyone's trousers though I'd think a rat might manage it (very nasty).

As far as I know, ferrets are put down the trouser legs (but only during competitions).