Elżbieta

Elżbieta is a very common Polish name. There were 518782 women with this first name in the whole Polish population in January 2020. It's in the top 10 of the most common Polish feminine middle names and, also in January 2020, 355808 women in Poland had this middle name. However, as for current popularity for babies this name is doing much worse right now. Last year (2019), it was in the top 200 most popular first names for baby girls in Poland, and 174 baby girls were named this. Eliza is much more in favour with parents now. As a very traditional and classic name though, with long history of usage, it's still well liked as a middle name and 1120 girls were given this as a middle name, which means it's still in the top 20.
For most Polish people with whom I've ever talked about this name, it seems to feel rather dated. It had a lot of usage in the first half of 20th century (but also was very common earlier than that) as well as in 50's and 60's. After that, its popularity appears to have started declining, and although now is the time for grandma names like Helena, Zofia or Maria to come back, Elżbieta hasn't got its time in the limelight just yet. Perhaps because it had more usage in the 50's and 60's than the afore mentioned Helena or Zofia so it does feel dated to many people without feeling as vintage as the other two.
Just as this name has many variants across different languages and cultures, it also has a fair few variants in Polish. It's archaic form was Halżbieta, with the diminutive Halszka. Halżbieta, as far as I am aware, isn't in use anymore, but Halszka works now as a separate (albeit rare) name. There is also Eliza, which used to only be a diminutive of Elżbieta but evolved into a standalone name. Same with Liza and Elza, though these are much rarer. And of course there is also Izabela and Izabella which share roots with Elżbieta. There are plenty of other nickname options as well. But the vast majority of Elżbietas these days, or at least the ones I know go by Ela. Other nicknames include, but are not limited to: Elżbietka, Elka, Elcia, Elunia, Lunia, Elusia, Lusia, Elżunia, Elżusia, Eli, Bietka, Bieta, Beta, Betka, Elizka, Elisia, Lizka, Lizia, Elizia etc.
Since there are plenty of saint Elizabeths, Elżbieta has plenty of name day options. Some of them are: 18th June, 8th July or 5th or 18th November, or on Halszka's name day (2nd March) or Eliza's (14th June, 17th August), or Izabela's (23rd February, 16th March, 31st August, 3rd September.

Elżunia (ehl-ZHOO-nya) is also used as a diminutive.

Other variants of the name:
Elka, Elżunia, Elcia, Eli, Eliś, Elunia, Elisia

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I'm often called Eli and Elisia, but that's rather rare in usage ;)

Also a Lithuanian name, featured by the Teta Elzbieta (Aunt Elizabeth) in "The Jungle", a classic from the 1930s. [noted -ed]