Apart from royalty, this name was only moderately popular in France during the Middle Ages. After the French Revolution, when Louis XVI was guillotined, it became less common.
The Normans brought the name to England, where it was usually spelled Lewis, though the spelling Louis has been more common in America. Famous bearers include French scientist Louis Pasteur (1822-1895), French actor Louis de Funès (1914-1983), Scottish author Robert Louis Stevenson (1850-1894), who wrote Treasure Island and Dr Jekyll and Mr Hyde, and American jazz musician Louis Armstrong (1901-1971).
Heinrich was popular among continental royalty, being the name of seven German kings, starting with the 10th-century Henry I the Fowler (the first of the Saxon kings), and four French kings. In France it was usually rendered Henri from the Latin form Henricus.
The Normans introduced the French form to England, and it was subsequently used by eight kings, ending with the infamous Henry VIII in the 16th century. During the later Middle Ages it was fairly popular, and was generally rendered as Harry or Herry in English pronunciation. Notable bearers include arctic naval explorer Henry Hudson (1570-1611), American-British novelist Henry James (1843-1916), American automobile manufacturer Henry Ford (1863-1947), and American actor Henry Fonda (1905-1982).