early 15c., from grand, adj. + father, n., probably on analogy of French grand-père. Replaced grandsire and Old English ealdefæder. Grandfather clause originally (1899) referred to exemptions from post-Reconstruction voting restrictions (literacy, property tax) in the U.S. South for men whose forebears had had the right to vote before 1867 (thus allowing poor and illiterate whites to continue to vote). Grandfather clock is c.1880, from the popular song; they were previously known as tall case clocks or eight-day clocks.