shoe-leather (n.)

Old English leðer (only in compounds) "tanned or otherwise dressed hide or skin of an animal," from Proto-Germanic *lethran (source also of Old Norse leðr, Old Frisian lether, Old Saxon lethar, Middle Dutch, Dutch leder, Old High German ledar, German Leder), from PIE *letro- "leather" (source also of Old Irish lethar, Welsh lledr, Breton lezr). As an adjective from early 14c.; it acquired a secondary sense of "sado-masochistic" 1980s, having achieved that status in homosexual jargon in the 1970s.

In commercial and popular usage leather does not include skins dressed with the hair or fur on: such skins are usually distinguished by compounding the word skin with the name of the animal from which they are taken: as sealskin, bearskin, otter skin, etc. In the untanned state skins valued for their fur, hair, or wool and destined to be tawed and dressed for furriers' and analogous uses, are called pelts or peltry. [Century Dictionary, 1900]

Middle English sho, "low-cut covering for the human foot," from Old English scoh, from Proto-Germanic *skokhaz (source also of Old Norse skor, Danish and Swedish sko, Old Frisian skoch, Old Saxon skoh, Middle Dutch scoe, Dutch schoen, Old High German scuoh, German Schuh, Gothic skoh). No known cognates outside Germanic, unless it somehow is connected with PIE root *skeu- "cover" (source also of second element in Latin ob-scurus).

The old plural form shoon lasted until 16c. The meaning "metal plate or rim nailed to the hoof of a horse or beast of burden to protect it from injury" is attested from c.1300. The distinction between shoe and boot (n.) is attested from c. 1400.

To stand in someone's shoes "see things from his or her point of view" is attested from 1767. Old shoe as a type of something worthless is attested from late 14c.

Shoes tied to the fender of a newlywed couple's car preserves the old custom (mentioned from 1540s) of throwing an old shoe at or after someone to wish them luck. Perhaps the association is with dirtiness, on the "muck is luck" principle.