More info about the name "Johnna"
Johna is a feminine form of John and is ultimately based on the same origin as Joan. Joan originates in Hebrew language and means "God is merciful". It is a feminine form of John and as a female name has been used since the 17th century. One of the most famous bearers of this name was Joan of Arc, Maid of Orleans, a French heroine who led the French army in the Hundred Years' War. She was burned by the English at the stake for heresy and later on declared a martyr.