Anglicized form of Carolus (see Charles), or of its feminine derivative Carola. It has never been common as a boy's name, and has become even less so since its growth in popularity as a girl's name. This seems to be of relatively recent origin (not being found much before the end of the 19th century). It probably originated as a short form of Caroline.
German: probably an altered form of Dümmler or Thümmler, a nickname for a noisy, unruly person or an occupational name for a traveling entertainer, from Middle High German tumelen ‘to move quickly or irregularly’.