"muscle contraction," late 14c., from Old French crampe, from a Frankish or other Germanic word (cf. Old High German krapmhe "cramp, spasm," related to kramph "bent, crooked"), from a Proto-Germanic root forming many words for "bent, crooked," including, via French, crampon. Writer's cramp is first attested 1842 as the name of a physical affliction of the hand, in reference to translations of German medical papers (Stromeyer); also known as scrivener's palsy.
"metal bar bent at both ends," early 15c., from Middle Dutch crampe or Middle Low German krampe, both from the same Proto-Germanic root that yielded cramp (n.1). Metaphoric sense of "something that confines or hinders" first recorded 1719.