Why do they call the upsidedown cake cake?

The term "upside-down cake" refers to a cake that is baked with fruit, such as pineapple or cherries, placed in the bottom of the pan and caramelized. When the cake is baked and inverted, the fruit ends up on top.

The name "upside-down cake" comes from this inverted presentation after baking. The fruit is placed upside down in the pan before baking, and then flipped over right side up to serve, with the fruit facing upwards.

So, the name isn't a reference to any particular ingredient or technique, but rather the visual effect of the fruit being on top of the cake after it's been flipped.