1818, "to act as a pontiff, say pontifical Mass," from Medieval Latin pontificatus, past participle of pontificare "to be a pontifex," from Latin pontifex (see pontiff). Especially "to assume pompous and dignified airs, issue dogmatic decrees" (1825). Meaning "to say (something) in a pompous or dogmatic way" is from 1922. Related: Pontificated; pontificating.
early 15c., "tenure of a pope;" 1680s, "time during which a pontifical office is held by a particular incumbent," from Old French pontificat and directly from Latin pontificatus "office of a pontiff," from pontifex (see pontifex).