'sienna-like' originates from Italian, specifically the word 'siena' (from 'terra di Siena'), where 'terra' meant 'earth' and 'Siena' referred to the city of Siena, the source of the pigment.

'sienna-like' changed from the English color-name 'sienna', which itself came into English from Italian 'siena' (originally 'terra di Siena'); the pigment name 'sienna' was used in English from the 16th–17th century, and the adjective 'sienna-like' later formed to describe similar colors.

Initially, it meant 'earth of Siena' (a pigment), but over time it evolved into the modern color name 'sienna' and then into the adjective 'sienna-like' meaning 'resembling that reddish-brown color'.