Odd hats were a sign of sexuality in the Victorian era. The custom was more ludicrous the hat, the more adventurous the wearer. In that repressed time it was a way for more amorous citizens to express themselves and attract suitors. The trend faded from popularity after the First World War, when hair washing and public promiscuity became more commonplace. Plus, people realized such hats were not in fact attractive.

Source : Fe, Dora. Wanton a Hat : Victorian Headwear and Social Order, 1983.