Part of the Mitzvah Tanz ceremony is to hire a Badchan who sings in rhyme the praises of the individuals he calls up for the dance. The Minhag is, the person who was called up, will hand over a monetary tip to the Badchan.
The origin of this Minhag goes back to the times of the Rishonim.
The Minhag was for the Chazzan to attend weddings and sing a Mi Shebeirach for each guest. It was expected from the guest to pay the Chazzan.
The Agodos Maharsha (Ta’anis 16 D.H.Beiso) is very much against this practice. He considers it Gezeilah and not a Matana. (The guest never asked for a Mi Shebeirach, and must hand over money unwillingly to the Chazzan)
Going back even earlier in history, Reb Yehuda Hachasid was also against this practice.
The Or Zarua (113) quotes R. Eliezer Mibhim(Bohemia) who wrote to R.Y. Hachasid defending this Minhag. He says in most towns in Poland, Russia and Hungary they are not Lomdei Torah. It is necessary to hire a Chazzan to be their Shliach
Tzibbur , Moreh Tzedek and teach the children. By not allowing them to earn additional monies at the Chasenes we won’t find Chazanim to do this job.