"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.
"to contract, afflict with spasms" (of muscles), early 15c., from cramp (n.1). Related: Cramped; cramping.
"to bend or twist," early 14c., from cramp (n.2) and Old French crampir "to bend, twist." Later "compress forcibly" (1550s), and, figuratively, "to restrict too straitly, confine or hinder the free action" (1620s). Meaning "to fasten, secure, or confine with a cramp" is from 1650s. To cramp (one's) style is attested by 1917. Related: Cramped; cramping.