English word detain comes from French tenir, Latin detinere, and later Old French detenir (To detain (to keep as a prisoner; to not allow to leave).)

Detailed word origin of detain

Dictionary entry	Language	Definition
tenir	French (fra)	(followed by the preposition à) to be attached to something, to be fond of something, to hold something dear. (intransitive) to stay; to hold. (reflexive) to behave. (reflexive) to hold oneself, to be standing. (reflexive) to maintain, remain in a certain position or disposition. (reflexive, Quebec, slang) to hang out. (reflexive, uncommon) to hold on. (transitive) to have; to hold. [...]
detinere	Latin (lat)
detenir	Old French (fro)	To detain (to keep as a prisoner; to not allow to leave).
detain	English (eng)	(transitive) To keep back or from; to withhold.. (transitive) To keep someone from proceeding by holding them back or making claims on their attention.. (transitive) To put under custody.. (transitive) To seize goods for official purposes.