Ideophonic for paralingual expression of agreement, compare typologically Arabic يَه ( yah ) developed with the exact same meaning at the Yemenite Red Sea coast.
*ja
yes ( confirmation particle )
thus , so
Proto-West Germanic: *jā Old English: ġēa , iā ; ġē Old Frisian: jē , gē ; jā , jē , jō Saterland Frisian: ja , jee West Frisian: ja Old Saxon: jā , giā ; ge , gi , gie , gia Middle Low German: ja , jâ Old Dutch: jā Old High German: jā Middle High German: ja , jā Alemannic German: ja , jaa , jòò , jä Bavarian:Cimbrian: ja Viennese: jå German: ja ( standard ) ; jo , joa ( informal ) → English: ya → Polish: jo Luxembourgish: jo Yiddish: יאָ ( yo )
Old Norse: já Icelandic: já Faroese: ja Norwegian Nynorsk: ja Norwegian Bokmål: ja Old Swedish: iā Swedish: ja → Finnish: jaa Danish: ja , jo
Gothic: 𐌾𐌰 ( ja ) , 𐌾𐌰𐌹 ( jai )