The lather effect is a drinking term that stems from a shampoo analogy. When you shampoo your hair the first time it takes a large palmful of shampoo to create a nice lather. However, after a quick rinse it merely takes a little drop to gain a full healthy lather. Similarly, if you drink hard the night before, it only takes a very small amount of booze to get you ripped the next morning.
This bloody mary has me all lathered up this morning.