1)
What is the meaning of "Hilulim"?
1.
Rashi citing Targum Yonasan: It is dances.
2.
Radak: It is Simchah. The banquet hall is called Hilula (Kesuvos 8a).
2)
What was the reason for the Hilulim (dancing or Simchah)?
1.
Malbim: They normally did so at the time of the grape harvest.