The story
From great- + grandniece.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A great-granddaughter of one's sibling, a granddaughter of one's nephew or niece. (Brother's great-granddaughter: fraternal great-grandniece. Sister's great-granddaughter: sororal great-grandniece) Full definition →
From great- + grandniece.
Etymology from Wiktionary, CC BY-SA 4.0.