I'm not being funny

Phrase

UK idiomatic

(UK, idiomatic) Used as a softening preface to a statement that might be taken as offensive or malicious.

Japanese Meaning

（英）攻撃的または侮辱的に受け取られる可能性のある発言の前置きとして、発言内容を和らげるために使われる表現。 / 自分の意見が誤解を招かないように、軽い言い回しで補足する意図を示す口語表現。

I'm not being funny, but if you leave those documents on the table again, they might get lost.

冗談ではないんですが、もしその書類をまたテーブルの上に置きっぱなしにすると、紛失してしまうかもしれません。

Sense（1）

(UK, idiomatic) Used as a softening preface to a statement that might be taken as offensive or malicious.

Clara: Well, I'm not being funny, but those clothes aren't really suitable for having meetings with clients.

John: Really?

Clara: I think so – a shirt and tie, or suit and shirt would be better.