Emily Dickinson Lexicon

MAR'ROW, n. [Sax. merg, mearh; D. merg; G. mark; Dan. marv; Sw. märg; Corn. maru; Ir. smir and smear; W. mêr, marrow; Ch. מרא mera, to make fat; Ar. to be manly. See Marl.]

1. A soft oleaginous substance contained in the cavities of animal bones.
2. The essence; the best part.
3. In the Scottish dialect, a companion; fellow; associate; match. Tusser.