Zacharias was a priest of the course of Abia (Luke 1:5) married to Elizabeth without children. Once an angel came to him and foretold that they were going to have a son called John. Zacharias, being an old man, did not trust the angel, so the latter made Zacharias to 'lose all power of speech' until the birth of the child (Luke 1:20). In due time the boy was born, Zacharias called him John, despite the protests of all the neighbors. His son was the future St. John the Baptist.
See: Fra Angelico. The Naming of John.
Giotto. Annunciation to Zachariah.