'pro-spiritualist' is a compound formed from the prefix 'pro-' (from Latin 'pro', meaning 'for' or 'in front of') and 'spiritualist' (from 'spirit' + the agentive suffix '-ist').

'spirit' originates from Latin 'spiritus', passed into Old French 'espirit' and Middle English 'spirite', becoming modern English 'spirit'; 'spiritual' developed from Late Latin 'spiritualis', and the noun 'spiritualist' arose (notably in the 19th century) to denote adherents of the Spiritualism movement; adding the prefix 'pro-' produced the compound 'pro-spiritualist'.

Initially, 'spiritualist' specifically referred to adherents of the 19th-century Spiritualism movement, so 'pro-spiritualist' originally meant 'in favor of Spiritualism'. Over time the compound has retained that basic sense and is used more broadly for someone who supports spiritualist beliefs or practices.