limber (adj.)
"pliant, flexible," 1560s, of uncertain origin, possibly from limb (n.1) on notion of supple boughs of a tree [Barnhart], or from limp "flaccid" [Skeat], or somehow from Middle English lymer "shaft of a cart" (see limber (n.)), but the late appearance of the -b- in that word argues against it. Related: Limberness. Dryden used limber-ham (see ham (n.1) in the "joint" sense) as a name for a character "perswaded by what is last said to him, and changing next word."
limber (n.)
"detachable forepart of a gun carriage," 1620s, from Middle English lymer (early 15c.), earlier lymon (c.1400), probably from Old French limon "shaft," a word perhaps of Celtic origin, or possibly from Germanic and related to limb (n.1). Hence, limber (v.) "to attach a limber to a gun" (1783). Compare related Spanish limon "shaft," leman "helmsman."
limber (v.)
1748, from limber (adj.). Related: Limbered; limbering.