the.com/grandad

means An affectionate, informal term for a grandfather.

from A diminutive of 'grandfather,' built the same way 'dad' sits under 'father' — the 'grand-' prefix comes from French grand (great), borrowed into English kinship terms to mark a generation up, as in grandmother, grandson. 'Grandad' (also spelled granddad) is the cozy, nursery-room version, shaped by the same impulse that gives us 'mum' and 'papa': small, repeatable sounds that toddlers can manage and everyone else keeps using out of affection.