'pro-Masonic' originates from the Latin prefix 'pro-' (from Latin 'pro') meaning 'for' or 'in favor of', combined with 'Masonic', which derives from English 'Masonic' < 'mason' (Old French 'maçon') where 'maçon' meant 'stone-worker'.

'pro-Masonic' arose by combining the prefix 'pro-' with the adjective 'Masonic' in the 19th century (used especially in political and social contexts as a counterpart to the 'Anti-Masonic' movement) and eventually became established in modern English as the adjective 'pro-Masonic'.

Initially it simply meant 'for Freemasonry' in a general supportive sense, but over time it also took on connotations of being 'supportive of the organization, its members, or their political/social influence'.