It’s Greek for “feast of fifty.” In Hebrew, the celebration is called Shavu’ot. Commemorating God giving Moses the Ten Commandments (and the rest of the Mosaic Law) on Mount Sinai, which according to tradition was 50 days after the Passover.
The feast of Pentecost was a perfect moment for the Christian church to be born, because Jewish worshipers were gathered to Jerusalem from all over the ancient world. When the disciples started speaking in tongues from the Upper Room, people were shocked to hear mysteries in their native languages, and the power of God was poured out freely on the streets, effectively starting Christianity. Even more importantly, thousands started believing in Jesus and took that belief back with them to their home countries once the feast was over, and spreading the new movement across the Roman empire like a wildfire...
It does indeed mean ‘count fifty’... of course from Passover. Now, what was the instruction Peter gave at that Pentecost gathering... Peter made the prophet Joel one and the same as the ‘Gospel’... What did Joel pen? Oh, at that Pentecost in Acts ... people understood the tongues spoken, there was no need of an interpreter. This ‘reenactment’ is not on the schedule until the ‘elect’ are delivered up to allow the Holy Spirit to speak through them .... no premeditation as what to say is allowed.