I have been unable to find a definition, or a source for the word mertilize. I've seen it used on TV, in articles, and even in comic strips.
Assuming it's the same word I've heard and seen many times in cartoons and old movies, the word is "murderlize" and as it's defined in the Dictionary of American Slang.
It is a variation on a threat to cause bodily harm to someone, but said in a funny way..."I'll murderlize you!"
It is a slang term meaning "to destroy or annihilate". Usually, this destruction is done in a fantastical way with a heavy leaning on science-fiction elements.
It is not a very common term and the earliest usage I could find was Calvin and Hobbes from January 2009:
I think the word you may be thinking of is "marmalise".
EDIT: In spite of a downvote, I'll press on.
"Marmalize", from Wiktionary: "To thrash", "To defeat decisively". Alternative spelling "Marmalise".
In the UK we never really had the Three Stooges so can't comment, but as someone who is exposed to Looney Tunes cartoons virtually every day, this is unquestionably the word that Bugs Bunny uses, "Why I'll marmalize ya!". Also, many of the other characters use it on the same context.