For some context, according to wikipedia, the following serve as examples of 副助詞:
Adverbial particles (副助詞, fuku-joshi) ばかり, まで, だけ, ほど, くらい, など, なり, やら
Question: Why are adverbial particles (副助詞) called "adverbial" (副詞) particles?
Is it that all of these sorts of particles can combine with nouns (or noun phrases) to form adverbs (副詞)? Is that the defining feature of what it means to be an 副助詞?
Here りんごばかり ("only apples") is acting as an adverbial phrase which modifies 食べています?
EDIT: I am also trying to understand the dictionary definition of 副助詞 from goo:
However this part is confusing me:
If I'm reading this correctly, 副助詞 can only come after 用言や活用連語 (conjugatable words) to form something that is adverbial? But can't 副助詞 come after pure nouns (as in 「りんごばかり」, where りんご is a non-conjugatable word) to form adverbial phrases too? If that's the case, why is the definition emphasizing 用言や活用連語 here?