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In the sentence "Boy, is there a lot to answer for" (from a recent EL&U comment), "boy" is used for expressing a strong reaction, especially admiration or excitement.
How did this meaning/usage come about? It doesn't seem to be some sort of minced oath, and an association with the pejorative term "boy", used to mean "black male", seems a bit far-fetched.
The suggested dupe fails to satisfactorily explain the origin of the term. It's easy to explain how "Gee" is a minced version of "God", but I don't see such a pathway for "boy". And the condescending sense suggested doesn't explain why "Oh, boy" expresses pleasure or excitement.