'entirely-separated' originates from the combination of 'entirely' and 'separated', where 'entirely' means 'completely' and 'separated' means 'divided or disconnected'.

'Entirely' comes from the Old French word 'entier', meaning 'whole', and 'separated' comes from the Latin word 'separatus', meaning 'to divide'.

Initially, 'entirely-separated' meant 'completely divided', and this meaning has largely remained the same in modern usage.