“Ish kabibble” is the usual way the expression appears.
Some, however, write it as a solid word, ishkabibble, and others make it three words, ish ka bibble.
Actually you may spell it as you wish, for, like the Missouri mule, it has no pride of ancestry and no hope of posterity.
Its source, that is, is unknown.
It sprang into popularity roughly about 1915, and was long thought to be a Yiddish phrase equivalent to “I should worry”, meaning “it is of no concern to me”, which came into vogue at about the same time.
But the Jews disclaim the saying.
In fact, the usual Yiddish expression is, Es is mein daige, “It is my worry.”