'ethnohostile' is a modern compound formed from the combining form 'ethno-' (from Greek) plus the English adjective 'hostile.' 'Ethno-' comes from Greek 'ethnos' meaning 'people, nation,' and 'hostile' comes from Latin roots meaning 'enemy.'

'Hostile' traces back through Middle English and Old French from Latin 'hostilis' (from 'hostis' meaning 'enemy'). The combining form 'ethno-' was adopted into English from Greek in the 19th century to form compounds relating to ethnic groups; the compound 'ethnohostile' is a 20th/21st-century coinage combining these elements.

Initially the roots referred to 'people/nation' (ethnos) and 'enemy' (hostis); over time, combining 'ethno-' with 'hostile' produced a descriptive adjective meaning 'showing hostility toward ethnic groups,' a specific modern usage.