1) Wright has examples of this word in the late 1800s and gives the meaning ‘a leather patch on the toe of a boot or clog’: the verb meant to mend or patch shoes.
The following earlier references support those definitions and point to a possible wider use, which may be linked with the noun ‘capping-leather’: 1642 Coblers ... have nowe vjd a day and theire meate, because capping leather is soe deare, Elmswell
1674 he wanted some nails to mend the cappell of his hand staff, Cannon Hall
1770 shoo soald and heelespecht and 3 capils
shoes mended o’th toos and capild, Meltham. Earlier still, in 1617, a new caple was in a list of tools In the milne at Ripley but the meaning is not clear. A horse could be a ‘caple’ but that meaning seems unlikely in this case. It is worth noting though that ‘capel’ was said by Halliwell to be the horn joint of a flail and Wright has ‘caplin’ as a leather loop serving the same purpose.