The word 'valid' originates from the Latin adjective validus, meaning 'strong, powerful, effective,' which itself derives from the verb valēre, 'to be strong, be well, have power.' This core sense of strength and effectiveness was applied in legal and logical contexts in Late Latin and French, shifting from physical power to the power of an argument or the binding force of a contract. The modern English meanings of 'logically sound' and 'legally acceptable' thus preserve the original notion of something possessing inherent strength and worth.

Structure: val (strong, worth) + id (adjective suffix) 'val' is from Latin valēre (to be strong, be worth). '-id' is an adjective-forming suffix from Latin -idus.