I found this, it's nearly a two year old answer to a similar question asked on Yahoo. Or somewhere. It's credited to a weird pseudonym name, so I cut and pasted below. This doesn't quite answer the question, but does highlight a peculiarly British tendency to over complicate things.
Just before I post it, a lot of where one sat in the theatre comes back to class. Now considered the best seats in the house, and priced as such to reflect that, the orchestra or stalls used to be the 'cheap' seats. This is me just speculating, now, but as I read around, yes, a stall is alternatively defined as the place where you park/keep your horse. There is a hint of stalls being looked down upon as where the riff-raff sat, hence the 'low grade' name of stalls. just some random thoughts. If anyone knows better, PLEASE add to the debate and correct this!!!!
anyway, this is the post that was interesting I promised to post five hundred paragraphs ago....
"The terminology of UK theatre seating is anything but simple. For example, at the Royal Opera House you have the orchestra stalls, stalls circle, grand tier, balcony, amphitheatre, and lower and upper slips. At the Coliseum, on the other hand, you have the stalls, the
dress circle, the upper circle, and the balcony. he orchestra stalls and stalls are the same thing, but the Coliseum has no equivalent to the stalls circle, as it has stalls boxes, which the ROH does not have.
The grand tier is equivalent to the dress circle, and then, most confusingly of all, the ROH balcony is equivalent to the Coliseum upper circle, and the ROH amphitheatre is equivalent to the Coliseum balcony. The Coliseum does not have slips. One of the most common configurations is to have stalls, dress circle, and upper circle. But
then the Theatre Royal Drury Lane has a grand circle where one would expect a dress circle, in addition to an upper circle and a balcony. he Victoria Palace also has a grand circle, but this time it is the name given to the second circle, while the first circle retains the
term dress circle. At the Duke of York's the first circle is called the royal circle. The Harold Pinter also has a royal circle, but this time it replaces what would have been the upper circle, and the first circle is called the dress circle. The Lyceum has both a royal circle and a
grand circle.
Anyway, stalls essentially refers to seating that is at ground level."
Further speculation: ground level. Groundlings. Commoners, the lot of them!
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Phillip Goodchild
Theatre Arts Instructor/Assistant Department Head of English
Hillsborough County Schools
Ruskin FL
Original Message:
Sent: 10-30-2015 15:46
From: Joanne Karr
Subject: "stalls"
Does anyone know why the British call the "orchestra" seats of a theatre "the stalls"?
Sent from my iPhone