Not a clue, but how about this one?

Some days ago I realised that there has got to be a word that wife number one would use for wife number two in a harem, and vice versa. Tampting to think of Arabic words but in fact Europe also has quite a tradition of Poly-relationships so there has got to be an English word too. Hardly a word I will ever need but curriousity got the best of me so I just had to ask.

Now that I am asking anyway, how would husband number one call husband number two?