"Juba Jew" was the name of an African American dance step from the early 1920s or earlier. That dance steo was mentioned in the version of "Juba" that was collected by Thomas W. Talley.

JUBA
Juba dis an' Juba dat,
Juba skin dat yaller Cat. Juba! Juba!

Juba jump an' Juba sing.
Juba, cut dat Pigeon's Wing. Juba! Juba!

Juba, kick off Juba's shoe.
Juba, dance dat Jubal Jew. Juba! Juba!

Juba, whirl dat foot about.
Juba, blow dat candle out. Juba! Juba!

Juba circle, Raise de Latch.
Juba do dat Long Dog Scratch.

-snip-

According to Talley's comments in his now classic 1922 book Negro Folk Rhymes-Wise and Otherwise, skin dat yaller Cat, cut dat Pigeon's Wing, Long Dog Scratch, and Jubal Jew were all names of African American dance steps.

"There is a variety of Dance Rhyme to which it is fitting to call attention. This variety is illustrated in our collection by "Jump Jim Crow," and "Juba." In such dances as these, the dancers were required to give such movements of body as would act the sentiment expressed by the words while keeping up the common requirements of beating these same words in a tattoo upon the ground with the feet and executing simultaneously a graceful dance."

Thomas Washington Talley (originally published New York: The Macmillan Company, 1922; p 231; 1968 edition)


I'm uncertain where that dance name Jubal Jew came from, or how that dance was done. However, "Juba" was used as a personal name for African American males and "Jubal" may have also been an African American male personal name. Perhaps the Jubal Jew was imitating the movements of a Black Jew. I'm only being a little bit facetious.