...is pishposh/tosh related to poppycock?
"Oh, pishposh!"
"Oh, poppycock!"

Welllll ... pishtosh is dismissive as in "Now you're just being silly." Or, that you are adding something that has no relevancey to the discussion.
Whereas poppycock is a more cutting statement that you talking bullsh*t.
Lestaways® that's the way I figure it.