I may be misremembering, but wasn't there actually some game thread where to find the significance of a particular uncommon phrase, one googled it, only to find the game thread was its only occurrence?
Perhaps i'm imagining things...
Anyway, i submit as a definition of schtish, something entertaining but with sufficient repetition causes one's yearnings for creativity to respond "ish", i think. Specifically worded to work for schtick too. Did i do good?