scruff (n.) Look up scruff at Dictionary.com
"nape of the neck," 1790, altered (by influence of scruff "crust") from scuft (1787), probably related to North Frisian skuft "back of the neck of a horse" and Dutch schoft "withers of a horse," from a common Germanic source (compare Old Norse skopt "hair of the head," Gothic skuft, Middle High German schopf, German Schopf). Another theory holds it to be a variant of scurf.