h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A piper is a variety of potato, so "eleven pipers piping" could refer to eleven "piping" (hot) potatoes -- a must for any true love's Christmas meal.

I can't help but wonder if this isn't so much a message from the potato lobby as one from the plumbing lobby. Having 10 Lords, 9 ladies, 8 maids, plus the assorted livestock all in one place, I would think the sanitary facilities would be overextended. Hence, one would need more pipes to accomodate the plumbing requirements. If all this occurred within 12 days, then one would need these facilities quickly, and I believe the current union requirement for such a job is 11 men.