pasch
The feast of Passover or (specifically) the Paschal Lamb, or (for Christians), Easter, seen as the fulfillment of Passover.
archaic
And on the first day of the Azymes, the disciples came to Jesus, saying: Where wilt thou that we prepare for thee to eat the pasch? But Jesus said: Go ye into the city to a certain man, and say to him: the master saith, My time is near at hand, with thee I make the pasch with my disciples.
The Paschal Mystery; the death and resurrection of Jesus.
archaic
The Man-God had scarcely returned to His Father when the Apostles hastened to establish a solemn festival to commemorate His pasch, that is to say, His glorious passage from death to life.
Where it comes from
Borrowed from Latin pascha. Perhaps also influenced by Old Norse páskar and its derivatives.
Adapted from the Wiktionary entry pasch (CC BY-SA 4.0).