Origin: 1675–85; perhaps short for shamble-legs one that walks wide (i.e., as if straddling), reminiscent of the legs of a shamble1 (in earlier sense “butcher's table”)
"to walk with a shuffling gait," 1681, from an adj. meaning "ungainly, awkward" (1607), from shamble (n.) "table, bench" (see shambles) perhaps on the notion of the splayed legs of bench, or the way a worker sits astride it. Cf. Fr. bancal "bow-legged, wobbly" (of furniture),