DARK CHAMBER

The word chamber was borrowed around the beginning of the 1100s from the Old French word chambre, which comes from Latin camera, which had the same definition but also had a specific  connotation of the rooms having vaulted ceilings. That's from Greek kamara, which described anything with an arched cover, and kamara in turn is reconstructed as deriving from the Proto-Indo-European root khem, meaning "bend" or "curve". If you noticed the word camera and wondered if there's any relation to photography, there actually is: our modern word is actually a clipping of the Latin phrase camera obscura, which meant "dark chamber", because the first cameras used a dark room and a pinhole.  According to Google NGrams, usage of the word camera peaked in the early 2000s and is now in decline.