stirp (n.)

"race, lineage, family," c. 1500, from Latin stirp "the stock of a family, line of descent, ancestral race," a figurative use from stirps "stem, stalk, trunk of a plant," figuratively "source, origin, foundation, beginning," a word of uncertain origin. De Vaan writes that it "Has been compared with Lith. stirpti 'to grow up, grow high', sterptis 'to stiffen', which is a possible but not compelling semantic connection."

OED reports that it "became obsolete in the 17th c. and reappears (in affected literary use) about the middle of the 19th." Hence stirpiculture "breeding of special stocks or strains, production of pure races by careful breeding" (1869). The form stirps seems to be that used in law (1680s).