"to hold back," early 14c., from a Scandinavian source, such as Old Norse stemma "to stop, dam up; be stopped, abate," from Proto-Germanic *stamjan (source also of Swedish stämma, Old Saxon stemmian, Middle Dutch stemon, German stemmen "stop, resist, oppose"), from PIE root *stem- "to strike against something" (source also of Lithuanian stumiu, stumti "thrust, push"). Not connected to stem (n.). Related: Stemmed; stemming. Phrase to stem the tide is literally "to hold back the tide," but often is confused with stem (v.2) "make headway against."
Verbal phrase stems from (1932, American English), perhaps is from stem (v.) in the sense "to rise, mount up, have origin in" (1570s), or is influenced by or translates German stammen aus, probably from a figurative sense represented by English stem (n.) in the sense of "stock of a family, line of descent" (c. 1540; compare family tree, and German stammvater "tribal ancestor," literally "stem-father").