also readmit, 1610s, from re- "back, again" + admit. Related: Readmitted; readmitting.
late 14c., "let in," from Latin admittere "to allow to enter, let in, let come, give access," from ad- "to" (see ad-) + mittere "let go, send" (see mission). Sense of "to concede as valid or true" is first recorded early 15c. Related: Admitted; Admitting.