'separatism' originates from French, specifically the word 'séparatisme', which was formed from 'séparer' (to separate) plus the suffix '-isme' (equivalent to English '-ism'). The French root ultimately goes back to Latin 'separare', where 'se-' meant 'apart' and the root meant 'to sever/divide'.

'separatism' entered English via French 'séparatisme' and was formed by adding the English suffix '-ism' to 'separate' (from Latin 'separare'). Over time the word took on a specifically political sense in modern usage.

Initially related broadly to the act or condition of separating ('the state of being separate'), but over time it evolved into the current specialized meaning of a political doctrine or movement advocating separation or secession.