I didn't know this word could also mean 〇〇. It was news to me.
I had no idea 〇〇 could also refer to XX.
1) I didn't know this word could also mean 〇〇. It was news to me.
「この単語が〇〇って意味もあるとは知らなかった。初耳だな。」
It was news to me. で「初耳です。」
2) I had no idea XX could also refer to 〇〇.
「XX(この単語)が〇〇のことを指すとは知らなかったよ。」
refer to で「〜のことを言う。〜を指す」
ご参考になれば幸いです!