As I understand it, the whole "midsummer" thing comes from the Celts--the people who inhabited just about all of Europe that wasn't the Mediterranean, Scandinavia, or the Germanic tribal lands. In their calendar, there were just two seasons--summer and winter. Summer went from Spring Equinox to Fall Equinox. So the summer solstice was midway between the two--which made it "middle of summer"!
As I understand it, the whole "midsummer" thing comes from the Celts--the people who inhabited just about all of Europe that wasn't the Mediterranean, Scandinavia, or the Germanic tribal lands. In their calendar, there were just two seasons--summer and winter. Summer went from Spring Equinox to Fall Equinox. So the summer solstice was midway between the two--which made it "middle of summer"!