The end of the name -ke is an indication for Germans of a person who is coming from the east. In Polish the name ending is -ek or -ski, like Wanski. So the German spelling for Wanski would be Wanske.
According to the Dictionary of American Family Names, Oxford University Press, ISBN 0-19-5098137-4, Juhnke is from the Czech Junek, a diminutive of Jun. Jun is a Czech nickname for a lively young man (juny). This is ultimately cognate with the French Jeune and the English Young.
To a German, the Juhnke name might mean something similar to a lively young man coming from the east, possibly from the Polish or Czech area.
If the name Juhnke is written in Polish with the German u umlaut and without diacritical marks, it could become Junke. It is not known if those with the name of Junke and Juhnke are from the same family. Both names appear in the Pommerania area, but the Junkes and the Juhnkes appear to be separate families.
Hanna Junke, the wife of Carl Bartz, spelled her name without the h. She is not any known relation of Carl F. W. Juhnke.