Ja Brdom is a Serbian folk song with an associated dance. Here’s a school group from Užice, Serbia:
And another YouTube from a Serbian performing group in Calgary, Canada:
As published in Ron Houston’s excellent article in Folk Dance Problem Solver, 1992, the lyrics are:
Ja brdom, brdom, brdom, a devojka dolom, dolom, Ja brdom, brdom, brdom, a devojka dolom.
“I am walking the high road, and the girl the low road.”
//Ja okum, okum, okum, a devojka skokom, skokom,//
“I am eyeing, eyeing, eyeing, and the girl hopping, hopping, hopping.”
//Ja dolom, dolom, dolom, a devijka šorom šorom.//
“I walk the low road, and the girl the village street.”
However, only the first verse matches what’s being sung in the above YouTubes.
Ron goes on to quote Dick Crum: “Crum told us that this kolo was popular at weddings, fairs and other village social events in and around the town of Užica (oo’-zhee-tsah) in the Republic of Serbia. The word ersko is derived from ero (air’-oh), a nickname applied by other Serbians to people from the Užice area.” “He also told us that Ersko Kolo was one of the first dances taught to school children in Yugoslavia in the 1950’s”.
In 2017, whether looking for You Tubes of the song Ja Brdom, or the dance Ersko Kolo by Serbians, the results are the same. I find performances only by children.
As you can see, the choreography varies widely. The common features are movements to the right & left during the slow part, and in and out of centre during the fast.