Why (interj.) - Tradução em português

I've always been somewhat intrigued by a rare and unclear (to myself, that is) use of the word 'why'.

The first time I got in touch with it, was in one of Shylock's Monologues in Shakespeare's 'Merchant of Venice'

"Revenge! If a Christian wrong a Jew, what should his sufferance be by Christian example? Why, revenge! The villainy you teach me I will execute, and it shall go hard but I will better the instruction."

For a long time, I forgot it was even used. 'Till I heard someone, using it with the similar intention, I thought.

Now I'm trying to figure how can we translate this to portuguese.

the dictionary says: interj. Used to express mild surprise, indignation, or impatience.

I'll believe this is an Interjection, although I'm not totally sure.

Given the dictionary's entrie, I'd translate as 'RAIOS!'. But I'm still not much confident.

thanks in advance.