'cool-toned' originates from modern English as a compound of 'cool' and 'toned'; 'cool' comes from Old English 'cōl' meaning 'not warm' and 'tone' (from Latin 'tonus' via Greek 'tonos') came to be used for 'tone' or 'shade' of color in English.

'tone' passed from Greek 'tonos' into Latin 'tonus' and then into English as 'tone' with meanings including pitch and later color shade; 'cool' developed from Old English 'cōl' (from Proto-Germanic roots); the compound 'cool-toned' emerged in the 20th century in fashion and color terminology to describe color undertones.

Initially the elements meant 'not warm' ('cool') and 'tone/pitch' ('tone'); over time the compound came to specifically denote 'having cool color undertones' especially in cosmetics and fashion contexts.