Here are some possible interpretations:
* "Derndest" might be a misspelling of "dearest": This is the most likely option.
* "Derndest" could be a regional dialect variation of a word: Some dialects have unique pronunciations and spellings. It might be a variation of a word like "dearest" or "dear" that's common in a specific region.
* "Derndest" could be a made-up word: It's possible that someone created the word for a specific purpose, perhaps in a fictional story or a joke.
To understand what "derndest" means, you need more context. If you provide the sentence or situation where you encountered this word, I might be able to offer a more specific answer.