'causa' originates from Latin, specifically the word 'causa', where it meant 'cause, reason, case.'

'causa' passed into Old French as 'cause' and into Middle English as 'cause'; the Latin form 'causa' has been retained in legal and scholarly Latin phrases and is sometimes used directly in English contexts.

Initially it meant 'cause, reason, or legal case' in Latin; over time the general sense continued in the descendant English word 'cause', while the direct Latin form 'causa' became more specialized (legal, historical, or scholarly use) in modern English.