patrol n.

late 14c., patin, "a wooden shoe or clog," later especially a thick-soled shoe worn by women to make them seem taller, from Old French patin "clog, type of shoe" (13c.), probably from pate "paw, foot," from Gallo-Roman *pauta, ultimately perhaps imitative of the sound made by a paw. The immediate source has been sought in Celtic [Barnhart] and Germanic [OED], but evidence is wanting. Likely cognates include Provençal pauta, Catalan pote, Middle Dutch and Dutch poot, German Pfote "paw." Also "an ice-skate" (1610s).

From the beginning of the eighteenth century, a peculiar device was used for the same purpose, formed of an iron ring with two or more uprights, supporting a wooden sole which was thus lifted several inches above the ground. This ringed patten has been used in England until a recent time, but has been little known in the United States. [Century Dictionary, 1895]

"police constable on a particular beat," 1841, from patrol (n.) + man (n.).