oakum (n.) Look up oakum at Dictionary.com
"loose fiber obtained from taking apart old hemp ropes," early 15c., from Old English acumba "tow, oakum, flax fibers separated by combing," literally "what is combed out," from Proto-Germanic *us-kambon (source of Old High German achambi); first element cognate with Old English a- "away, out, off;" second element from stem of cemban "to comb," from camb "a comb;" from PIE *gembh- "tooth, nail" (see comb (n.)).