Contrary to what they seem to be saying over at Irish Pagan School, apparently the summer solstice was kind of a big deal way back into ancient times. It wasn't just because they were celebrating the longest day. It was also because this was about the time that last year's harvest was starting to run out.
The really poor people lived almost entirely on potatoes for most of the year, but about this time the potatoes were starting to run out and the new ones weren't ready yet. In order to fill the gap, they grew cabbage, which has a much shorter growing season. They actually had to eat so much of it that their skin in the summertime had sort of a greenish-yellow color.
People think of the Great Famine in the 1840s because everybody knows about it and it was so huge and catastrophic, but there were also a bunch of other famines that happened earlier than that. They were just shorter and less widespread.
Eventually, the summer solstice festival was Christianized and changed to St. John's Day or St. John's Eve on June 23rd because, of course, they had to change everything, but not too much. People believed that if you didn't burn a bonfire on St. John's Eve, your crops would be unlucky that year. St. John's Eve was also a big festival day going back as early as the 1300s.
Another sad thing that happened during the solstice festival, and later on St. John's Eve, was that farmhands would be hired out. Kids as young as twelve or thirteen were often hired out as labor. How they were treated pretty much depended on wherever they landed. Some families were good to them and treated them like another one of the kids. Other families treated them worse than their work animals.
It wasn't just that people were hoping the kids would earn wages to send back home. It was also a way to send them away for the summer and get them fed somewhere else because these families didn't have enough resources. Sending the children out to work temporarily reduced the number of mouths to feed until the next harvest.