late 14c., "change of one substance to another," from Medieval Latin trans(s)ubstantiationem (nominative trans(s)ubstantio), noun of action from trans(s)ubstantiare "to change from one substance into another," from Latin trans- "across" (see trans-) + substantiare "to substantiate," from substania "substance" (see substance). Ecclesiastical sense in reference to the Eucharist first recorded 1530s.
