Latin, literally "wonderful to relate," from neuter of mirabilis "wonderful, marvelous, extraordinary; strange, singular" (see marvel (n.)) + ablative supine of dicere "to say, speak" (from PIE root *deik- "to show," also "pronounce solemnly"). The expression is found in Virgil. Mirable "wonderful, marvelous" was used in English 15c.
slang phrase meaning, more or less, "I don't care, I don't worry," 1913, 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]