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.
German: from Middle High German kīl ‘wedge’, ‘wooden peg’, hence possibly a metonymic occupational name for a maker of such pegs or for a wood chopper. Alternatively, it may be nickname for an uncouth or misshapen person (compare Keidel) or a topographic name for someone who lived on or near a wedgeshaped plot of land.