The term First Lady was first used for what president wife?

The term "First Lady" was first coined by President Zachary Taylor in 1849 whil eulogizing Dolly Madison. The first White House occupant to be called "First Lady" was by The Bachelor President James Buchanan referring to his niece Harriet Lane who was actually occupying that position. In the media, Frank Leslie in his Illustrated Monthly in 1860, was first to print , "The Lady of the White House, and by courtesy, the First Lady of the Land." Since Harriet Lane, the term "First Lady" went to all predecessors of her position.

The title was first used in print for Mrs. Rutherford Hayes.