The state, condition, or experience of being a grandmother, including all the roles and relationships involved.
From grandmother (grand- + mother, with grand from Old French meaning 'great') plus -hood, a suffix meaning state or condition. The term emerged in modern usage to parallel fatherhood and motherhood.
The word grandmotherhood became really common in the 1900s as societies started recognizing family roles more formally—before that, people just called it 'being someone's nan'!
Complete word intelligence in one call. Free tier — 50 lookups/day.