HellZaPoppin

“Popularised by the 1938 theatre musical Hellzapoppin’, and by the 1941 film Hellzapoppin’ based on the former, the one-word form hellzapoppin’ represents a colloquial pronunciation of the phrase hell’s a poppin’…The phrase hell’s a poppin’, and its variants, mean events are unfolding in a chaotic manner; a state of confusion and disarray is taking hold.”

From the interesting Wordhistories site:

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https://wordhistories.net/2021/11/14/hellzapoppin/#:~:text=The%20phrase%20hell%E2%80%99s%20a%20poppin%E2%80%99%2C%20and%20its%20variants%2C,synonymous%20phrase%20%28all%29%20hell%20breaks%20loose%20and%20variants.