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?
E.g.
りんごばかり食べています。
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:
ふく‐じょし【副助詞】 の解説
助詞の一。種々の語に付き、それらの語にある意味を添えて、副詞のように下の用言や活用連語を修飾・限定する類の助詞。現代語では「さえ」「まで」「ばかり」「だけ」「ほど」「くらい(ぐらい)」「など」「やら」など、古語では「だに」「すら」「さへ」「のみ」「ばかり」「など」「まで」など。
However this part is confusing me:
副詞のように下の用言や活用連語を修飾
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?