Koi!
 

I understand it can mean a form of love (different from the word 'ai' (愛)). I also understand it as a fish (鯉). However - and I'm somewhat embarassed to admit this - I've seen people use something that sounds very similar to "koi" on TV shows, as a way of beckoning before a fight.

Maybe it's ko-i...? I'd be lying if I were to say I was certain.
I'm not sure how to phrase my question properly... But can someone please explain this to me? Or am I listening to it wrong afterall?

You ain't listenin' to it wrong, dude. (Dang, is my English a-changing!?)

It's 来い , the imperative form of the verb　来る（くる） = to come.

And about that form of love, that is 恋. It looks love-related, doesn't it?

Ah, I see now.
Thank you very much.

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