Where does “twinness” come from?

twinness (English) comes from English twin, from Middle English twin, from Old English twīn, from Proto-West Germanic twiʀn, from Proto-Germanic twiznaz, from Proto-Indo-European dwisnós, from Proto-Indo-European dwóh₁ — two.

twinness (English): The state, quality, or condition of a twin;...

Definitions

  1. The state, quality, or condition of a twin;...

Ancestry of “twinness”, step by step

twinness traces back through two separate lines of ancestry.

via English twin

StepLanguageWordMeaning
1EnglishtwinEither of two people who shared the same uterus...
2Middle Englishtwin
3Old Englishtwīndouble thread, twist, twine, linen-thread, linen
4Proto-West Germanictwiʀntwine, double thread
5Proto-Germanictwiznazthread, twine
6Proto-Indo-Europeandwisnósdouble
7Proto-Indo-Europeandwóh₁two

via English Ness

StepLanguageWordMeaning
1EnglishNessAn Ulster princess and the mother of Conchobar mac Nessa and Findchoem in the Ulster Cycle of Irish mythology. Daughter of Eochaid Sálbuide. Also the mother of Cormac Cond Longas by incest with Conchobar mac Nessa
2Middle Englishnesse
3Old Englishnæsnot, not at all; not; first/third-person singular...
4Proto-Germanicnasjąfoothill; headland; cape
5Proto-Indo-Europeannéh₂snose
Every word from Proto-Indo-European dwóh₁