AlpheccaStars“ The expression refers to a person who can drink a lot of alcohol and not become
visibly inebriated.
"A fifth" is the standard size for a bottle of whiskey or other hard liquor - it used to be 1/5 gallon; now 750 ml
”
Visibly is the key-word here. People I know in AA tell me that, except for the size of a person, the result of similar amounts of alcohol consumed affects most people about the same, as far as mental ability and quick-response actions are concerned. But, I'm no doctor.