'even-toned' originates from English, specifically formed as a compound of the adjective 'even' and the noun 'tone'. 'even' comes from Old English 'efen' meaning 'level' or 'equal', and 'tone' comes ultimately from Greek 'tonos' (via Latin 'tonus' and Old French 'ton') meaning 'pitch' or 'stretch'.

'even' developed from Old English 'efen' into Middle English 'even' with the sense 'level, equal'; 'tone' came from Greek 'tonos' to Latin 'tonus' then Old French 'ton' and Middle English 'tone'. The modern compound 'even-toned' arose in Modern English by combining these elements to describe uniformity of tone in voice or color.

Initially, 'even' meant 'level or equal' and 'tone' meant 'pitch or sound quality'; combined, the phrase came to mean 'having a uniform pitch/quality' and extended by analogy to uniform color or general steadiness.