The idiom "to trip the light fandango" was already in usage in the US as a phrase for carefree dancing in a Spanish or Latin American fandango style by the time of World War II (see, for example, its usage in the recording "South America", Vitaphone Release 1460A, 1945).

What does it mean to trip the light fandango? Okie... think carefully first, then make a decision:
The relevant sentence in the passage is: The idiom "to trip the light fandango" was already in usage in the US as a phrase for carefree dancing in a Spanish or Latin American fandango style by the time of World War II (see, for example, its usage in the recording "South America", Vitaphone Release 1460A, 1945). So, the answer is carefree dancing in a Spanish or Latin American fandango style by the time of World War II.