stem (n.) Look up stem at Dictionary.com
O.E. stemn, stefn "stem of a plant," also "either end-post of a ship," from P.Gmc. *stamniz (cf. O.S. stamm, O.N. stafn "stem of a ship;" Dan. stamme, Swed. stam "trunk of a tree;" O.H.G. stam, Ger. Stamm), from PIE base *sta- "to stand" (see stet). Meaning "support of a wineglass" is from 1835. Stem-winding watches (1875) were advanced and desirable when introduced, hence slang stem-winder "excellent thing" (1892). The nautical sense is preserved in the phrase stem to stern "along the full length" (of a ship), attested from 1627. The verbal phrase stems from, first recorded 1932, Amer.Eng., translates Ger. stammen aus, probably from a fig. sense represented by Eng. stem (n.) in the sense of "stock of a family, line of descent" (c.1540; cf. family tree, and Ger. stammvater "tribal ancestor," lit. "stem-father").
stem (v.) Look up stem at Dictionary.com
"to hold back," c.1300, from O.N. stemma "to stop," from P.Gmc. *stamjan (cf. Swed. stämma, O.S. stemmian, M.Du. stemon, Ger. stemmen "stop, resist, oppose"), from PIE base *stem- "to strike against something" (cf. Lith. stumiu "thrust, push"). Phrase to stem the tide is lit. "to hold back the tide," but often is confused with stem (v.) in sense of "to make headway against, head in a certain course" (late 14c.), which is from stem (n.)).