Other forms: grandfathers, grandfathered
Your grandfather is your mother's father or your father's father. My grandfather, a great-grandfather, grandfather clock.
English uses one word where many languages distinguish the two sides. Grandad, grandpa, grandpop and pops are the affectionate forms. A grandfather clock is the tall freestanding pendulum kind, named after a song of 1876. To grandfather a rule means to let existing cases carry on under the old terms, which is standard in regulation. Note grandfather clause.
1noungrandfatherThe father of your mother or father.
“His grandfather lived to about ninety-four.”
2verbexemptTo exempt existing cases from a new rule.
“Drivers who already had old cars were grandfathered in under the new pollution rules.”
Too few real examples of this word to estimate which sense is commonest.
grandfather is a relative.
Also accepted in games: grandpa, granddad
Middle English grandfadre is graunt, great, plus fader, modelled on French grand-père. It replaced the older English ealdfaeder.
Proto-Indo-European
*gʰer-
Middle French
grandpere
Middle English
grandfadre
English, today
grandfather
Built from
The noun is derived from Middle English grandfadre, graundfadir, graunfadir, grauntfader, and other forms, from graunt (“big, large; great, important”) + fader (“male parent, father; remoter male ancestor”), probably modelled after Middle French grandpere, grant pere (“male parent; remoter male ancestor”) (whence French grand-père); the English word is analysable as grand- + father. Superseded earlier eldfather, elderfather. The verb is derived from the noun.
Etymology from Wiktionary, CC BY-SA