'ash-grey' originates from English as a compound of 'ash' and 'grey'. 'ash' comes from Old English 'æsc' meaning 'ash (residue from burning) or ash tree', and 'grey' comes from Old English 'grǣg' meaning 'grey (colour)'.

'ash' remained largely unchanged from Old English 'æsc' (ash/ash tree), while 'grey' evolved from Old English 'grǣg' (from Proto-Germanic *grēwaz). The compound form 'ash-grey' developed in modern English to name a specific shade.

Initially each element simply named 'ash' and 'grey'; combined, 'ash-grey' came to denote specifically the pale grey colour resembling ash and has been used as a colour-name in modern English.