frost-nail1
/ˈfrɒs(t)neɪl/Farriery. Now somewhat rare and chiefly historical
noun
A nail with a large sharp head, inserted into a horseshoe in place of a regular nail to provide extra traction in frosty conditions.
Origin
Middle English. From frost + nail.
frost-nail2
/ˈfrɒs(t)neɪl/Now rare (archaic in later use)
verb
[with object] To equip (a horse) with horseshoes which are fitted with frost-nails. Also with the horse's rider as object. In later use usually in pass. Compare frost.
Origin
Late 16th century; earliest use found in Hugh Platt (bap. 1552, d. 1608), writer on agriculture and inventor. From frost-nail.