This close to the beginning of the COVID19 pandemic we can still remember what it was like before. Antecovidian times: when toilet paper was fully stocked, paying gigs were scheduled, and we all practiced basic hygiene.
Wait... apparently not everyone was doing that last one? Yikes. Anyway, the prefix 'ante' means before, and 'diluvian' refers to the biblical Flood. Yeah, capital 'F' Flood. You know the one. Antediluvian means the time period betwixt the fall of humans and the Flood narrative in Genesis. In secular use it can just mean that something is way out of date or out of style, like sex-role stereotypes or cuffed jeans.
Hopefully human decency and ethical decision making doesn't go the way of the unicorns.
