"blue laws"

[Cohen, Gerald Leonard]

If "blue laws" derives from "blue" (= Puritanical), why does "blue" have this meaning?  Are we sure that "blue" (= Puritanical) existed prior to the coining of "blue laws"?  Or could could "blue" (= Puritanical) derive from the "blue" of "blue laws"?

Gerald Cohen
P.S. I don't have my dictionaries handy. Maybe the answer is clear there.

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