From Wiktionary, the free dictionary

From its popularity among jazz musicians.

jazz dot (plural jazz dots)

1. A soul patch.

   • 2005, Michael Segell, The Devil's Horn: The Story of the Saxophone, from Noisy Novelty to King of Cool, Farrar, Straus and Giroux, →ISBN:

     The jazz dot or soul patch, the tuft of hair beneath the lower lip, is so common among “cats” who can play as to almost be considered a part of the saxophone embouchure.

   • 2013, Barrie Jean Borich, My Lesbian Husband: Landscapes of a Marriage, Graywolf Press, →ISBN:

     [...] men with gray beards or homegrown dreadlocks or a sandy jazz dot on the chin, gathered around platters of organic turkey or homemade lasagna ...