What's the "een" in Halloween?
1530s, from Middle French réhabilitation and directly from Medieval Latin rehabilitationem (nominative rehabilitatio) "restoration," noun of action from past participle stem of rehabilitare, from re- "again" (see re-) + habitare "make fit," from Latin habilis "easily managed, fit" (see able). Specifically of criminals, addicts, etc., from 1940.
1570s, "to bring back to a former condition after decay or damage," back-formation from rehabilitation and in part from Medieval Latin rehabilitatus, past participle of rehabilitare. Meaning "to restore one's reputation or character in the eyes of others" is from 1847. Related: Rehabilitated; rehabilitating.
rehabilitate re·ha·bil·i·tate (rē'hə-bĭl'ĭ-tāt')
v. re·ha·bil·i·tat·ed, re·ha·bil·i·tat·ing, re·ha·bil·i·tates
To restore to good health or useful life, as through therapy and education.
To restore to good condition, operation, or capacity.
In politics, the restoration to favor of a political leader whose views or actions were formerly considered unacceptable. (Compare nonperson.)