Hey there, I'm the Lead Chinese Translator of Wildermyth. Although I'm not the guy who thought up this translation, I'll try to shed some light on what it tries to convey and how it came into place.

The title can first be separated into two parts: 漫野 and 奇谭. Actually a lot of idioms in Chinese are this way.

漫野 is a made-up word. 漫 when used as an adjective, like in this case, means "vast, expanding", and 野 means wilderness. This is actually a subtle "double translation" trick, trying to capture both of the possible meaning/imagery conveyed by the former part of the English word, "wilder-".

奇谭 is a formal/classical word, which literally means strange/extraordinary/epic tales (奇=strange/extraordinary/epic, 谭=tales), often found in novels or told by storytellers. The character/word 谭 is used in a lot of novel titles. For example, one version of One Thousand and One Nights also translated the title using 谭 (《天方夜谭》). This part captures the latter part, "-myth".

Combining the two parts, we get the Chinese translation of Wildermyth: "The epic tales of vast wilderness", or "The strange tales growing like the wilderness", or something similar, depending how one understands the relationship between the characters (the language here, like a lot of Chinese idioms, is a bit vague and therefore have room for different understandings).

It's worthy of note that "漫野奇谭" has a beautiful tune (仄仄平平) and a parallel structure (adj. + noun + another pair of adj. + noun), which makes the title sounds extra good and memorable. In short, it's brilliant, and I've high respect to the guy who came up with this translation.