is derived from the Greek word πεντηκοστή/pentēkostḗ for “fiftieth” (meaning: the 50th day), and is employed in the Septuagint for the Jewish feast of Weeks (Shavu’ot; Feasts and festivals: II; III; Tob 2:1), 50 days after the feast of Unleavened Bread. Originally an agricultural celebration of grain harvest ending, it became the second of three Jewish pilgrim feasts (between Unleavened Bread and Booths). Eventually it was associated with the giving of the Law to Moses on Sinai.
In the New Testament, Pentecost is the day the Holy Spirit (Spirit/Holy Spirit…