'blackish' originates from Old English, specifically the word 'blæc' (meaning 'black') combined with the suffix '-ish' from Old English '-isc', meaning 'of the nature of' or 'having the quality of'.

'blackish' developed from Old English 'blæc' + '-isc', passed through Middle English forms such as 'blac(ish)', and eventually became the modern English adjective 'blackish'.

Initially it meant 'having the quality of black' (i.e., black in color); over time the suffix -ish produced a sense of approximation, so the modern meaning is 'somewhat black' or 'tending toward black'.