Where did the quote "Madam, where is thy Lochinvar" originate?

Answer 1

The play, "Bus Stop," by William Inge.

Published 1956, Dramatists Play Service, Inc.

Here is an addendum as to the source of Inge's inspiration.

I think it likely that Inge was referencing "Marmion," the epic poem by Walter Scott. It's about the Battle of Flodden and was published in 1808. The stanzas about the story of Lochinvar were the most popular. Here are two of the most famous lines:

Oh, what a tangled web we weave
When first we practice to deceive!

There is also a poem by Scott titled "Lochinvar." Here are the first few stanzas.

OH! young Lochinvar is come out of the west,
Through all the wide Border his steed was the best;
And save his good broadsword he weapons had none.
He rode all unarmed and he rode all alone.
So faithful in love and so dauntless in war,
There never was knight like the young Lochinvar.

Answer 2

Actually, it's a line from one of the works of Moliere written in the 1600's.