'leftist' originates from modern English, formed by combining the word 'left' with the suffix '-ist', where 'left' referred to the left side or left-wing politics and the suffix '-ist' denoted an adherent or supporter.

'left' (meaning the side that is opposite of right) goes back through Middle English to Old English forms; the suffix '-ist' came into English via French '-iste' (from Late Latin/Greek), and the compound 'leftist' developed in English to name political adherents.

Initially, 'left' primarily denoted a direction or side; over time the term developed political meaning ('left-wing'), and 'leftist' came to mean someone who supports left-wing political positions.