To say that someone "can't drink fog" is to say they're a lightweight at drinking.
It's history comes from many a Kerry man who has emerged from a pub after many pints, is suddenly hit by the air and immediately feels more drunk
Euphemism describing the act of defecating, metaphorically speaking. Otherwise known as taking a good hard shyte for oneself. This particular expression is used when the excrement is of a particularly large and solid nature.
