Thomas Kirkman was a very smart man who lived a long time ago. He liked to solve puzzles and came up with a really cool puzzle called the "Kirkman's Schoolgirl Problem".
The puzzle was about schoolgirls who walked in groups of three every day. Kirkman wanted to figure out how he could make sure that the schoolgirls walked in different groups every day, so they could all be friends instead of just hanging out with the same people all the time.
He worked really hard and figured out a way to make sure that the groups of schoolgirls were different every day. This made him very famous and people all over the world started to know his name.
So, Thomas Kirkman was a really smart man who loved puzzles and created a cool puzzle about schoolgirls that made him famous.