Morganatic Marriages.—Morganatique

What is the derivation of this word, and what its *actual signification*? In the *Dictionnaire de l'Académie Française* (ed. 4to., 1835), the word does not appear. In Boister's *Dictionnaire Universel* (Bruxelles, 1835) it is thus given:— "Morganatique, *adj. 2 g.*, nocturne, mystérieux, entrainée par séduction; (mariage) mariage secret des princes d'Allemagne avec une personne d'un rang inférieur." And the same definition is given by Landais (Paris, 4to., 1842), but this does not give the derivation or literal signification of the word "*morganatic*." It is not in Johnson's *Dictionary*; but…