Emily Dickinson Lexicon

SAP, n.¹ [Sax. sæp; D. zap; G. saft; Sw. saft, safve; Dan. saft, sæve; Fr. seve; Arm. sabr; probably from softness or flowing. Qu. Pers. زَبَه zabah, a flowing.]

1. The juice of plants of any kind. The ascending sap flows in the vessels of the alburnum or sap-wood, and is colorless, while the descending sap flows in the vessels of the liber or inner bark, and is often colored. This remark however is applicable to exogenous plants only. From the sap of a species of maple, is made sugar of a good quality by evaporation.
2. The alburnum of a tree; the exterior part of the wood, next to the bark. [A sense in general use in New England.]