Pteridomania is a big word that means people really liked ferns a long time ago. It was a fad, kind of like when everyone loved fidget spinners a few years ago.
Back then, around the 19th century, people started to go crazy over ferns. They wanted to collect them, grow them, and decorate their homes with them. People became so obsessed with ferns that many started to go into the wild and find new kinds of ferns. They would collect them and bring them home.
People started to buy ferns for their homes and gardens too. It was considered very fashionable to have ferns, they were kind of like a status symbol. Some people even built special fern houses, called Wardian cases, so that they could grow ferns indoors.
But this craze didn't last forever. People started to lose interest in ferns as they found new things to obsess over. Today, ferns are still popular, but not as much as they were during the pteridomania era.