[int_19h]

> A lot of references to "first sleep" can be found if you search digitized records with that string and its foreign language equivalents, but so can references to obviously non-systematic things like "first injury" or "first marriage"

This hypothesis would also have to explain why we don't say things like "first sleep" anymore, even though we do say things like "first injury" or "first marriage".

[notahacker]

We don't talk about first sleeps but you'll still find plenty of modern references to "first sleep", "second sleep" and even "third sleep" in modern text too, from book titles to scholarly articles on sleep cycles