strap (n.)youdaoicibaDictYouDict
1610s, "band of leather," from Scottish and/or nautical variant of strope "loop or strap on a harness" (mid-14c.), probably from Old French estrop "strap," from Latin stroppus "strap, band," perhaps via Etruscan, ultimately from Greek strophos "twisted band; a cord, rope," from strephein "to turn" (see strophe). Old English stropp, Dutch strop "halter" also are borrowed from Latin, and the Old English word might be the source of the modern one. Slang meaning "credit" is from 1828.
strop (n.)youdaoicibaDictYouDict
mid-14c., "loop or strap on a harness," probably from Old French estrop, making it the older and more correct form of strap (n.), replaced by it from 16c. Specific sense of "leather strap used for sharpening razors" first recorded 1702. The verb in this sense is from 1841. Related: Stropped; stropping. Distribution of senses between strap and strop is arbitrary.