1913, "I should worry," of unknown origin, but perhaps derived from Yiddish nisht gefidlt. Said to have been popularized by comedienne Fanny Brice (1891-1951), but earliest references do not mention her.
"Chicken pox doesn't poison the wellsprings of one's existence like 'Ish kabibble,' and 'I should worry.!' Do you think it's any fun to bring up children to speak decent English, and then have their conversation strewed with phrases like that and with ain'ts? Do you think I like to hear Robert talking about his little friends as 'de guys' and 'de ginks?' [Mary Heaton Vorse, "Their Little Friends," in "Woman's Home Companion," February 1916]
An exclamation of indifference, nonchalance, etc: ''Ishkabibble,'' or ''I should worry''/It was a pretty abrupt transition from la belle epoque into the Space Age, but ish kabibble
[1921+; origin unknown; perhaps an alteration of Yiddish nit or nisht gefidlt; apparently introduced and perhaps coined by the comedienne Fanny Brice]