Hint
Look, if you know what's good for you, turn on the lights yourself.
Pacifism, pact, and peace itself all come from the common root. So does pay... which is one way to pacify some enemies.
Solution
It's a pacifier! As you may have surmised, the Pacific Ocean is nominally "peaceful" as well, having been named that by Magellan. I suspect irony was involved.
There's no pacifier emoji (???), but congratulations to yesterday's solvers Zachary Z., Jacob C., Anna J., Maddy, Hazel, Connor, Peter M., Yana, Charlie, Jason, Mr. Gregg, and Dr. Yetman. Thanks to everybody who made a guess!
Ten years later, Dr. Shapiro revived Puzzle of the Day at Proof School, writing each day's puzzle on a name tag. After 600 puzzles or so, he was just starting to feel normal about students reading his chest all the time when campus closed and the puzzle, like the rest of our lives, moved online. New puzzles are posted daily on school days.
Want to catch up on old PotDs? There's an archive currently containing puzzles from March to December 2020.