loose fiber obtained by untwisting and picking apart old ropes, used for caulking the seams of ships.
Origin: before 1000; Middle English okome,Old English ācuma, variant of ācumba, literally, offcombings, equivalent to ā- separative prefix (see a-3) + -cumba (see comb1)
"loose fiber obtained from taking apart old hemp ropes," 1420s, from O.E. acumba "tow, oakum, flax fibers separated by combing," lit. "what is combed out," from a- "away, out, off" + stem of cemban "to comb," from camb "a comb;" from P.Gmc. *us-kambon, second element from PIE *gembh- "tooth, nail" (see