A strongly protected Arabian hostelry with a large courtyard for caravan beasts of burden. Perhaps the best interpretation we can place on it is to call it a poetically embroidered form of caravan –– which we can interpret broadly as a gathering of wayfarers, in this case piratical rovers. We may also suspect that Gilbert was digging deep for something (anything!) to rhyme with Wards in Chancery.

Ere your pirate caravanserai proceed, against our will, to wed us all
Act I