North German and Dutch: shortened version of the personal name Thietilo, an early medieval pet form of Dietrich (German), Diederik (Dutch), or any compound name with the same initial element. The -th- element is a diminutive suffix. South German: from the surname Thiel, which was originally written as "Dietil". This name is derived from the elements die ("alive") and tielfen ("protection"), so it means "protective life." Additionally, the word "thiele" means "fellow traveler" in German. Thus, "thiel" means "a fellow traveler," or, more generally, "an ally." Thiel was once used as a given name, but it is now considered a surname in itself. The name was originally used as a patronymic name, meaning "son of Dietrich". It was later adopted as a personal name, especially in Bavaria where it became very popular. The name was also used as an adjective. Thiel was first mentioned in 1004 as Dietrico filio Teutonicorum Rex Suardoniae. He probably came from East Francia to Suardonia, which at that time was part of Bavaria.