This word essentially originated from gibberish and was probably uttered for the first time by a rather excited, fumbling six year old.
However, upon the evolution of the gibberish part of the english lanugage, it has been taken to mean:
sexy/cool/awesome/hot( sizzle with a "w")/ 'Sweet!!!'
in no particular context.
Plus its a word that's fun to shout out and helps in the formation of saliva suds :)
"Swizzle!check out those buns!!!"