Sounds like a combination of "toss" (tosser, toss off) and "poppycock".

Hard word to find about. Apparently it's related to some kind of British comedy show. Likely an invented word with no literal meaning. After a little more searching, it looks like it's from the show "Black Books."

I have never heard of "tossycock". I think you must be referring, as Gary says, to "poppycock".

I've not heard of the saying "Tossycock". However, there is a saying in English "Poppycock" which is often used to describe something as being nonsense, or something that doesn't make sense. Hope this helps!