morganatic (adj.)

a word used to denote the marriage of a man of high rank to a woman of lower station with stipulations limiting her claims, also of the marriage of a woman of high rank to a man of lower station; 1727, from French morganatique (18c.), from Medieval Latin matrimonium ad morganaticam "marriage of the morning," probably from Old High German *morgangeba (Middle High German morgengabe) "morning gift," corresponding to Old English morgengifu (see morn + gift (n.) ).

In an unequal marriage between a man of royal blood and a common woman, this was a gift traditionally given to the wife on the morning after consummation, representing the only share she and her children may claim in the husband's estate. Also known as left-handed marriage, because the groom gives the bride his left hand instead of his right, but sometimes this latter term is used of a class of marriage (especially in Germany) where the spouse of inferior rank is not elevated, but the children inherit rights of succession. Related: Morganatically.