Hello, Blair - I was searching for that word myself, which led me to this thread.

I am your buyer on this piece. I can tell you that the pitcher itself was made by Loetz - it is form 158 (alternately 8035), and dates to 1899, according to the line drawings in the Loetz book. The decor is called Delphi. Thanks to Google, the best theory I have on the word Seugnot is that there was a famous confectioner and patisserie (pastry shop) in Paris that was in operation during the time this pitcher was made (located at 28 Rue du Bac), and my guess is that this pitcher may have been in use in the patisserie, and the name was either put there by the cafe itself, or done as part of a special order from the Loetz factory.
Warren