Remember last verse of Please To See The King, that odd carol sung by Martin Carthy & Steeleye Span , supposedly about the Wren, king of birds - tho there are several different & competing exegeses:

Old Xmas is past, Twelfth Tide comes the last
So we bid you adieu, Great joy to the New [ie presumably Happy New Year]

Twelfth Night [aka Epiphany, the 12th Day of Xmas of the song where the Lords come a-leaping or the drummers drumming, depending on yr version], has also been identified with Roman Bacchanalia, when everything was reversed, slaves were masters for a day &c — hence, some think, the title of Shax's comedy, 'Twelfth Night, or What You Will', in which everyone is disguised, nothing is as it appears, nobody [becoz of existence of identical twins] is who they appear to be — as Feste the Fool exclaims sarcastically at one point, but we, the audience, know, more accurately than he thinks, "Nothing that is so, is so!"