balk (n.)
O.E. balca "ridge, bank," from or influenced by O.N. balkr "ridge of land," especially between two plowed furrows, both from P.Gmc. *balkan-, *belkan- (cf. O.S. balko, Dan. bjelke, O.Fris. balka, O.H.G. balcho, Ger. Balken "beam, rafter"), from PIE *bhelg- "beam, plank" (cf. L. fulcire "to prop up, support," fulcrum "bedpost;" Lith. balziena "cross-bar;" and possibly Gk. phalanx "trunk, log, line of battle"). Modern senses are figurative, representing the balk as a hindrance or obstruction (see balk (v.)). Baseball sense is first attested 1845.

http://www.etymonline.com/index.php?term=balk

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