The Collaborative International Dictionary of English v.0.48:
Skainsmate \Skains"mate`\, n. [Perhaps originally, a companion in winding thread (see Skein), or a companion in arms, from skain a sword (see Skean).] A messmate; a companion. [Obs.] [1913 Webster] Scurvy knave! I am none of his firt-gills; I am none of his skainsmates. --Shak. [1913 Webster]