Old English seam "seam, suture, junction," from Proto-Germanic *saumaz (cf. Old Frisian sam "hem, seam," Old Norse saumr, Middle Dutch som, Dutch zoom, Old High German soum, German Saum "hem"), from PIE root *syu- "to sew, to bind" (cf. Old English siwian, Latin suere, Sanskrit syuman; see sew).
Meaning "raised band of stitching on a ball" is recorded from 1888. Geological use is from 1590s.