1520s, "honoring of a day or season by appropriate festivities," formed in English from celebrate, or else from Latin celebrationem (nominative celebratio) "numerous attendance" (especially upon a festival celebration), noun of action from past participle stem of celebrare. Meaning "performance of a religious ceremony" (especially the Eucharist) is from 1570s; that of "extolling in speeches, etc." is from 1670s.
