Upsot mean to tip or overturn something
https://www.wordnik.com/words/upsotAlternatively it could be an archaic past participle of upset, in this instance meaning "capsized", but was also slang for "drunk or intoxicated", perhaps by association with the British term "sot" (drunkard).
http://en.wikipedia.org/wiki/Jingle_Bells#cite_note-8