How well was alcoholism understood at a time when people drank chronically?

During the 19th century and before, bad water made drinking alcoholic drinks almost a necessity — in any case, people drank by modern standards a tremendous amount.

I am guessing that Fetal Alcohol Syndrome, despite the large number of cases that no doubt existed, was not well understood if only because it was so common; I know FAS is a fairly modern term.

Delirium Tremens (DTs) — is it possible that the chronic usage of alcohol made this ironically a rare condition, maybe observed on ships when the rum ran out and only became really common during prohibition?