'pro-Arab' originates from Latin, specifically the prefix 'pro' (from Latin 'pro') meaning 'for' combined with 'Arab', ultimately from Arabic 'ʿarab' referring to the Arab people.

'Arab' entered English via Medieval Latin (e.g. 'Arab(i)us') and Old French forms before becoming Middle English 'Arab'; the prefix 'pro-' comes from Latin 'pro' and has long been used in English to form compounds meaning 'in favor of', producing the modern compound 'pro-Arab'.

Initially it literally meant 'for the Arabs' (i.e., in favor of Arab people), and over time it has been used specifically as a political or descriptive label meaning 'supportive of Arab people, culture, or political causes'.