expression
and so on; and so forth; et cetera
An emphatic or playful extension of うんぬん (and so on), often used in casual speech or writing to trail off a list. It can carry a slightly dismissive or vague tone.
See also: 云々 (うんぬん)
彼は仕事が忙しいだの、給料が安いだの、うんぬんかんぬん言っている。
He's going on about how busy work is, how low the pay is, and so on and so forth.
新しい規則について、手続きが面倒だとか、うんぬんかんぬん文句ばかりだ。
Regarding the new rules, it's nothing but complaints about the procedures being a hassle and so on.
など is a simple, neutral particle meaning 'and so on' or 'etc.'; うんぬんかんぬん is a longer, more colloquial phrase that can imply the speaker is glossing over details.
Reduplicative extension of うんぬん (云々), itself from Chinese 云云 (yúnyún), meaning 'and so on'. The addition of かんぬん creates a rhyming, emphatic phrase.