During the killing of the firstborn of Egypt, God passed over the homes of the Israelites, sparing them (Exodus ch.12).
If you are asking what the Hebrew word for "Passover" is, it's pesakh (פסח). If you are asking for the meaning of the holiday, it is a celebration of freedom, commemorating the exodus from Egypt.
Passover = Pesach (פסח)
Passover is called "Pessa'h" in French. This is not a French word, but comes from Hebrew.
Passover already is an English word. The Hebrew word is Pesach.
The most usual greeting (by English speakers) would be "good yontif." The word yontif is the Yiddish variation of the original Hebrew yom tov, meaning literally good day, but meaning holiday. Others say "chag Pesach sameach" which is Hebrew and means "happy Passover."
Pasca (Πάσχα)
Since Passover is a single word, it does not have an acronym. Acronyms are only used for phrases, not for words.
Our Blessed Lord used the occasion of the Passover to institute the Lord's Supper: the most Holy Eucharist, commonly known as the Mass. The meaning that He gave to it came the following day, on Good Friday, when He offered His life on the cross for the redemption and salvation of all of us. Thus the meaning that He gave it was the sacrifice of Himself upon the cross. This meaning was always there as the old Passover meal re-presented the Passover in Egypt when God saved His people which was to foreshadow the great Passover when God saved His people through the wood of the cross.
The word "Passover" appears 83 times in the King James Bible.
"Paschal" is derived from the Latin word "Paschalis," which refers to Easter or the Passover. It is often used in relation to the Passover feast or Easter celebration in Christian liturgy.
"Zees" is the sound of the Yiddish word that comes from the German "Süss" meaning "sweet". "Zeesen Pesach" is a wish offered to another person for a sweet Passover. That said, it should be mentioned that this particular wish, though graciously and sincerely offered, is not customary for Passover. A "sweet" holiday would be offered far more often at Rosh Hashana. The customary wish at Passover is for a "kosheren Pesach" ... a kosher Passover.
Passover, lenten, paschal, quadragesimal...