Regardless of the origins, if an expression is applied to a different context, it might still cause subconscious associations to form in the human brain. If you hear "Dutch courage" often enough, you might subconsciously start to link the Dutch to cowardice. For a more modern example take the word "gay". It originally meant "happy". Then it meant "homosexual". As a result of that second meaning large numbers of people use the word as a synonym for "unlikable" or "bad". If somebody uses the word in a context like "that movie is gay", that reinforces the connection between the concept "bad" and the concept "homosexual".
Therefore what's important is not the origins of a word, but its current associations and effects: "my car was vandalized" is OK but "that movie is gay" is not.
Therefore what's important is not the origins of a word, but its current associations and effects: "my car was vandalized" is OK but "that movie is gay" is not.