Shucks

google

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late 17th century: of unknown origin.

wiktionary

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From shuck(“something valueless”), also alteration euphemistic of shit, influence of fuck

etymonline

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shucks (interj.)

expression of indifference, 1847, from shuck (n.) in the secondary sense "something valueless" (i.e. not worth shucks, attested in a separate source from 1847).