“Gut" means “good," and is the general word used before expressions of greeting, such as “gut morgen" (good morning) or “gut nacht" (good night). The word “yuntif," on the other hand, is derived from the Hebrew words “yom tov," literally meaning “good day." A “yom tov" is a holiday, so “gut yuntif" can be used generically as an expression of greeting on any holiday, including Rosh Hashana, Yom Kippur, Sukkos, Pesaḥ, and Shavuos.
Although this expression is often heard on Saturday night after Shabbos (the Sabbath) has ended, it can also be used the night after a holiday. Literally meaning “good week," it shows a differentiation between the holiness of the Sabbath or holiday and the rest of the week.
A Guten Moyaid
Sukkos and Pesaḥ both contain days of ḥol hamo’ed, or “non-holy of the holiday." The first and last day (or two, in the Diaspora) are true holidays, in which most work is forbidden, similar to the Sabbath day. The middle days are more holy than regular days, but less so than the days of true holiday. The holiday expression of greeting used on these days is “a guten moyaid," or “a good [non-holy of the] holiday."
L’shana Toyva Tikasevu V’Sayḥasemu
On Rosh Hashana, there is a special greeting – in addition to “gut yuntif" – that is often said. This phrase literally means “You should be written and sealed for a good year," and refers to the belief that a person’s fate for the coming year is written on Rosh Hashana and sealed on Yom Kippur. Note: The last two words of this holiday expression must be conjugated differently when speaking to a single male (tikasev v'sayḥasem), a single female (tikasevi v'sayḥasemi), or groups of females (tikasevna v'sayḥasemna).
A Freiliḥin Ḥanukkah
On Ḥanukkah, this holiday expression is a common greeting. It is used both verbally and in Ḥanukkah cards sent from one person or family to another. The word “freiliḥin" literally means “happy" in Yiddish.
A Freiliḥin Purim
Similarly to “a freiliḥin Ḥanukkah," this holiday expression is used to wish people a happy Purim holiday. It is said when seeing others on the holiday and is written as a greeting in shalaḥ manos, or friendly gifts, which are given on Purim.
A Kosherin Pesaḥ
The Pesaḥ is a bit different than the greetings on other holidays, as one major focus of the holiday is cleaning all leavened products (e.g., bread, crackers, cereals) from the house. We therefore wish that Pesaḥ should be “kosher," in that no leavened products should remain in the house after the cleaning process. This is one of the only holiday expressions in Yiddish used before the holiday, usually for the month or so before Pesaḥ.