It means square dance boss.
The word "boss" belongs to the jianghu black language, meaning the boss of a group. A lot of films depicting the Hong Kong triad society, often said "handle", but also from the lips of the dictionary, the original word is "helm handle", meaning the helm of the person.
Later, I don't know who turned it into "扛把子", but "揸fit人" and "扛把子" in the Cantonese subtitles have the same meaning, only that they are not the same in the Cantonese version and the Mandarin version. It's just that the Cantonese version and the Mandarin version say it differently, but the meaning is the same.
Self-indulgence has been the main feature of square dancing since its inception. People do not seek fame or fortune when they participate in square dances, they do it purely for self-entertainment. For example, most of the square dances on the 15th day of the first month of the Chinese New Year and during the morning exercise are spontaneous performances by the public.
The use of dance to express the art of emotion, so that the dancers inner emotion to vent, produce a spirit of pleasure, while the viewers also get the spirit of enjoyment, which makes the dancers to get the opportunity to express themselves, produce a sense of self-worth. This is the reason why square dancing is so entertaining, and why it has endured since its inception.