Английский словарь Webster - pentecost

(n.) A solemn festival of the Jews; -so called because celebrated on the fiftieth day (seven weeks) after the second day of the Passover (which fell on the sixteenth of the Jewish month Nisan); -hence called, also, the Feast of Weeks. At this festival an offering of the first fruits of the harvest was made. By the Jews it was generally regarded as commemorative of the gift of the law on the fiftieth day after the departure from Egypt.