What's the "een" in Halloween?
1590s (adj.), from up + stairs (see stair). The noun is first attested 1872. Meaning "characteristic of upstairs life" (in private rooms of a household, as opposed to servants' quarters) is recorded from 1942.
He [Halifax] had said he had known many kicked down stairs, but he never knew any kicked up stairs before. [Gilbert Burnet, supplement to "History of My own Time," from his original memoirs, c.1697]