Merriam-Webster Collegiate Dictionary - marrow

 I. noun  Etymology: Middle English marowe, from Old English mearg; akin to Old High German marag ~, Sanskrit majjan  Date: before 12th century  1.  a. bone ~  b. the substance of the spinal cord  2.  a. the choicest of food  b. the seat of animal vigor  c. the inmost, best, or essential part ; core personal liberty is the ~ of the American tradition — Clinton Rossiter  3. chiefly British vegetable ~  • ~y adjective  II. noun  Etymology: Middle English marwe, ~  Date: 1516 chiefly Scottish one of a pair