Like when you wash your hair a second time in a row you get much more lather. The lather effect refers to when you get intoxicated a second night in a row, you get much more intoxicated.

"So remember, my friends, if you’re going to rinse and repeat always beware the extra bubbles." -- From the movie "The Lather Effect"

(n.) or (v.)
The effect of not being able to get drunk because of a high-state of trashedness the night before.

If you have been highly wasted one night, and try to get inebriated the next night it will cost you a fortune because it's nearly impossible.

The term comes from trying to lather a loufah, but it will not lather if there is still soap in it from the day before.