From Old French Jo(h)anne, and so a doublet of Joan. This too was revived as a given name in its own right in the first half of the 20th century. It has to some extent been influenced by the independently formed combination Jo Anne.
North German: from Middle Low German klūt(e) ‘lump of earth’, ‘sod’, ‘clod’, hence nicknames for an ungainly, clumsy, or uncouth person; in some cases they may have been applied as a metonymic occupational name for a farmer. See also Kloth, Klotz.