crampon n.

"involuntary and painful muscle contraction," late 14c., from Old French crampe (13c.), from a Frankish or other Germanic word (compare Old High German krapmhe "cramp, spasm," related to kramph "bent, crooked"), from Proto-Germanic *kramp-, 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 discussions of translations of German medical papers (Stromeyer); also known as scrivener's palsy.

early 15c., "metal bar bent at both ends," from Middle Dutch crampe or Middle Low German krampe, from Proto-Germanic *kramp-. It is thus the same word as  cramp (n.1). Metaphoric sense of "something that confines or hinders" is attested by 1719.