'ashiness' originates from the English adjective 'ashy' plus the noun-forming suffix '-ness' (from Old English '-nes(s)'), where the stem 'ash' ultimately comes from Old English 'æsc' meaning 'ash' (the residue or the ash tree).

'ash' was Old English 'æsc', which became Middle English 'ash'; the adjective 'ashy' was formed by adding the suffix '-y' to mean 'like ash', and later the suffix '-ness' produced the noun 'ashiness' to denote the state or quality of being ashy.

Initially it meant 'like ash' or 'covered with ash'; over time it broadened to describe a grayish or pale coloration and, by extension, the dry, flaky condition of skin that produces an ashen appearance.