I think this can be questioned in various parts of history. It's a meme that as the Victorian women did not show their ankles, people would find their ankles "hot", as we today would consider breasts etc.
Is their any truth to this? To my knowledge, attraction is often born from sexual dimorphism, which doesn't apply to the ankles.
Were ankles actually considered sexy?
Short answer: yes. In the Georgian era for example, writers had a fascination with thighs (especially white, plump and hairless ones). Will Fisher has actually written intensely about the sexual practices of hetero and homosexual couples using thighs for sexual pleasure. These attractions did also occur alongside erotic associations with breasts and buttocks as we continue to see today. The butt is actually a good example of a feature whose attractiveness does not stem from sexual dimorphism. It might be a good guess to say the features can be linked to femininity (e.g. a hairless, dainty ankle) but we don’t really know for sure