From the eternal question "Which came first, the chicken or the egg?"

A question of cause-and-effect or sequence of actions, possibly unanswerable.

https://www.urbandictionary.com/define.php?term=chicken-or-egg

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A reference to the classic, epistemological (philosophical theory of knowledge) problem of determining the (efficient) cause and a corresponding product amongst entities that could be argued to fill either, opposing roles.

Used more colloquially to laugh off an impasse in which the solution to a problem cannot feasibly be made to precede and solve that problem until said problem is already solved. Really, it can be downright abused on any pickle, dilemma or conundrum.

https://www.urbandictionary.com/define.php?term=Chicken-egg+Problem