Given that most sets of puzzle letters have cropped up before during the history of Chihuahua, it sometimes surprises me when a word like this is queried, that it hasn't already been queried on a previous appearance. However in this case, seignior was making its debut appearance. And its last appearance, as a common word at any rate, since I have to agree that it's a word seldom used since the demise of feudalism some little time ago now.