noun
more than enough to drink; plenty to drink
Used when there is an abundance of alcoholic beverages, often in the phrase 飲みでがある (to be a hearty drinker or to have plenty to drink).
今日は飲みでがあるから、たくさん飲もう。
There's plenty to drink today, so let's drink a lot.
飲み放題 means 'all-you-can-drink' (a fixed price for unlimited drinks), while 飲みで refers to the abundance of drinks available.
Compound of 飲み (drinking) + 出 (amount that comes out), referring to the amount of drink available.