In reply to:

Any other words you can think of from our arabic neighbors?

Where would Western navies be without their admirals? Then of course, there's Arabic loanword to which I am allergic - alcohol. I wonder if you could clarify something for me. You mention algebra et al as being by-products of the Crusades. I always thought that they were obtained through the Moorish governance of Iberia, rather than through the Crusades to Palestine. Would you mind filling in this gap in my understanding?

As an aside on the matter of quarantine, I think that if you read the Mosaic Law, you will find that it had quarantine regulations which were quite advanced for the time. It may be a pity that the mediæval Church and State didn't think to apply them.