From Wikipedia, we read:
“Hava Nagila” (הבה נגילה) (lit. Let us rejoice) is a Hebrew folk song that has become a staple of band performers at Jewish weddings and Bar/Bat Mitzvahs.
The melody was taken from a Ukrainian folk dance-song from Bukovina (a variant of Hora). It uses the Phrygian dominant scale, common in music of Romania and Western Ukraine.
Read the entire Hava Nagila Wikipedia article.
Now, may I be so bold as to suggest you click over to the home page of Hava Nagila (The Movie) where you will be able to view and listen to a sample clip of Hava Nagila (The Movie) and more video clips. You will also read, in part,
Hava Nagila (The Movie) is a documentary romp through the history, mystery and meaning of the great Jewish standard. Featuring interviews with Harry Belafonte, Leonard Nimoy, Connie Francis, Glen Campbell, Regina Spektor and more, the film follows the ubiquitous party song on its fascinating journey from the shtetls of Eastern Europe to the kibbutzim of Palestine to the cul-de-sacs of America. High on fun and entertainment, Hava Nagila (The Movie) is also surprisingly profound, tapping into universal themes about the importance of joy, the power of music and the resilient spirit of a people.