a solemn festival of the Christian church, observed on the fiftieth day after Easter, in memory of the descent of the Holy Ghost upon the apostles in the visible appearance of fiery cloven tongues, and of those miraculous powers which were then conferred upon them. WHYTT

It is called Whitsunday, or White Sunday; because this being one of the stated times for baptism in the ancient church, those who were baptized put on white garments, as types of that spiritual purity they received in baptism. As the descent of the Holy Ghost upon the apostles happened upon the day which the Jews called Pentecost, this festival retained the name of Pentecost among the Christians.