What is the source for the Jewish/Yiddish name Zundel/Zindel? Does it have an origin in Jewish religious traditions?
Zundel was not a uniquely Jewish name and does not per se have any connection to the Judaic faith. Its origin is from Germanic languages:
(also Zündel): from a diminutive of Zunder, a metonymic occupational name for a seller of kindling wood, from Middle High German zunder ‘tinder’.
Alternatively, as a first name, Zundel is the diminutive of the Yiddish "zun" which means "son" (See, e.g., http://www.babynamespedia.com/meaning/Zundel ).
As per Bris Avos (8-33) and Sefer Ha'bris (page 318, paragraph 22) the name Zundel was used as a name for a boy born to an unmarried girl. Apparently it means "the little sin" or something like that. So if your name is Zundel you probably have some skeletons in your closet (or in your ancestor's closet) - if you go back far enough.