Although, leptos actually comes more from "leptos", which I think means thin or petite in Greek. The word "leap" is actually from German roots and "flatypus" is not a real word at all.
Platys (πλατὺς) is “wide” or “broad”; platypus (πλατύπους) is “wide-foot” in ancient Greek and referred to flat-footed people. “Platypus” came from their paddle feet.
Leptos (λεπτός) is sort of derived from a word meaning “peeled” like the husk of threshed grain, that came to take on the meaning of delicate, subtle, or small/thin in Attic Greek usage.
Kurtosis (κύρτωσις) comes from ancient Greek “a bulging.” Had it been a traditional word coming from Greek through Latin or French to English, it might have been cyrtosis, like in biology:
