Green’s Dictionary of Slang

(orig. US) a theatrical or cinematic première; also as v., to have a première, a first night.

1936		M. Levin Old Bunch (1946) 103: The last night the fuckn preems are a hunerd, two three hunerd bucks.
1951		Green & Laurie Show Biz from Vaude to Video 546: A boxoffice socko from its preem performance.
1958		T. Capote Breakfast at Tiffany’s 38: Snippings from gossip columns. Rusty Trawler and Holly Golightly two-on-the-aisle at ‘One Touch of Venus’ preem.
2004		Variety Slanguage Dict. 🌐 preem – (n.) an opening-night or premiere performance.