Calque of English "black box." Two senses migrated together: (1) the flight data recorder + cockpit voice recorder on aircraft (which is actually painted bright orange, not black, for visibility after a crash), and (2) any system whose internal workings are opaque, used widely in AI and engineering discussion.
memory
黑 (black) + 匣子 (small box/case). 匣子 itself is everyday Chinese for a small lidded container, think of an old jewelry box. The 子 suffix gives the word a colloquial feel, similar to English "the box."
