The latest video in the excellent series Words Unravelled, with RobWords and Jess Zafarris, is devoted to "contronyms and other 'onyms'". Most people are familiar with words such as synonym, antonym, pseudonym, acronym, but I hadn't met contronym, which means a word with two meanings that are in some way opposite. For example I might sanction someone, which would mark my disapproval, but I might also sanction a course of action, which would mean I gave it my approval.
The suffix -onyms is from the Greek for name, and there are quite a few -onyms apart from the ones about. Rob and Jess discuss a whole range of other other interesting -onym words.
I thought I'd explore a bit further and was intrigued to find a number that describe names for physical features of the landscape, each formed by taking an Ancient Greek word for the feature in question and adding -onym. These all refer to proper names, e.g. Helvellyn is an oronym, The Grimpen Mire is a helonym, The Black Forest a drymonym, and so on. Here are the words I managed to find.
agronym – field
anemonym – hurricane
drymonym – forest
helonym – swamp
hydronym – sea
limnonym – lake
oronym – mountain
spelonym – cave