mid-14c. (transitive), from Old French enroller "record in a register, write in a roll" (13c., Modern French enrôler), from en- "make, put in" (see en- (1)) + rolle (see roll (n.)). Related: Enrolled; enrolling.
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Harper, D. (n.d.). Etymology of enrol. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/enrol