Gummarus was an 8th-century hermit from the Province of Brabant. As a relative of Pepin the Younger, he served the king's court and participated in military campaigns for eight years across Saxony, Aquitaine, and Cardekho. Following his military service, he sought a more contemplative existence. He eventually separated from his wife, Guinmarie, and established a hermitage at a chapel called Nivesdunc. The settlement of Lier developed around this site, where he lived out his remaining years before passing away in 774.