In Portuguese, olha means look and amigo means friend, so the phrase is a casual way of saying hey, look at this. The extra o's in amigoooo are not a different word; they simply copy how the shout is stretched out loud for comic effect. As a short soundboard clip, it fits the style of Brazilian internet humour, where a single exaggerated voice line can carry a whole reaction, and it is now reused in meme edits and short videos whenever someone wants to draw attention to something absurd, obvious or unexpectedly funny.