Where does “leinne” come from?

leinne (Scottish Gaelic) comes from Scottish Gaelic leinn, from Scottish Gaelic sinn, from Old Irish sinni, from Old Irish sisni, from Old Irish snisni, from Proto-Celtic snisni, from Proto-Celtic snīs, from Proto-Indo-European nō̆s — we.

leinne (Scottish Gaelic): with us, by us