Old English rap "rope, cord, cable," from Proto-Germanic *raipaz (cf. Old Norse reip, West Frisian reap, Middle Dutch, Dutch reep "rope," Old Frisian silrap "shoe-thong," Gothic skauda-raip "shoe-lace," Old High German, German reif "ring, hoop"). Technically, only cordage above one inch in circumference and below 10 (bigger-around than that is a cable). Nautical use varies. Finnish raippa "hoop, rope, twig" is a Germanic loan-word.
To know the ropes (1840, Dana) originally is a seaman's term. Phrase on the ropes "defeated" is attested from 1924, a figurative extension from the fight ring, where ropes ...
