Etymology Dictionary

SAP (1),  the juice of plants.  (E.)   M.E. sap, Kentish zep, Ayenbite of Inwyt, p. 96, l. 5.—A.S. sæp, sap; Grein, ii. 397. + O. Du. sap, 'sap, juice, or liquor;' Hexham. + O.H.G. saf; G. saft (with added t). + Gk. ὀπός, juice, sap.   β. Curtius (ii. 63) connects these with Lat. sucus, Irish sug, Russ. sok’, sap; from a primary form SAKA or SWAKA; cf. Lith. sakas, gum on cherry-trees.   In this view, k has become p, as in other cases; cf. Lat. coquere with Gk. πέπτειν.   See Suck, Succulent.   Der. sap-less, sapp-y, sapp-i-ness; sap-ling, a young succulent tree, Rich. III, iii. 4. 71.

SAP (2),  to undermine.  (F.,—Low L.,—Gk.?)   'Sapping or mining;' Howell, Famil. Letters, vol. ii. let. 4.—O.F. sapper (F. saper), 'to undermine, dig into;' Cot.—O.F. sappe (15th cent., Littré), a kind of hoe; mod. F. sape, an instrument for mining.   Cf. Span. zapa, a spade; Ital. zappa, 'a mattocke to dig and delue with, a sappe;' Florio.—Low Lat. sapa, a hoe, mentioned A.D. 1183 (Ducange).   β. Diez proposes to refer these words to Gk. σκαπάνη, a digging-tool, a hoe; from σκάπτειν, to dig.   He instances Ital. zolla, which he derives from O.H.G. skolla.   Der. sapp-er.