From the Latin effetus, in turn from ex- and fetus. Originally, it meant weakened from giving birth.
In English it came to mean worn out or barren, and unable to bear young.
About 50 years ago, it started to take a strange turn -- probably due in large part to empty-headed society columnists, it began to be used to mean 'sophisticated'. You can still see it used in this way today.
These days it is often used to mean 'marked by self-indulgence, triviality, or decadence'. It is also sometimes used to mean 'overrefined' or 'effeminate'.