"The Merry Widow Waltz" was song in the The Merry Widow
(German: Die lustige Witwe) an operetta by the Austro-Hungarian
composer Franz Lehár.

In its English adaptation by Basil Hood, with lyrics by Adrian Ross,
The Merry Widow became a sensation at Daly's Theatre in London,
opening on 8 June 1907. The first American production opened on
21 October 1907 at the New Amsterdam Theatre on Broadway for another
very successful run of 416 performances, and was reproduced by
multiple touring companies across the US, all using the Hood/Ross
libretto.

The "Merry Widow" versions of "Pink Pajamas" song fit the opening
stanzas of the Waltz.

Listen here:

https://archive.org/download/a_20220711_20220711_0713/Orchestre%20ODEON%20%E2%80%93%20Merry%20Widow.mp3