Silly earthling.
(excerpt)
Similar to the Romulan cloaking device, the Klingons received this technology from the Romulans circa 2268, when the two civilizations shared a political alliance. The Klingons outfitted many ships, particularly their Bird-of-Prey type vessels with the devices.
I did not know that. I’ve always seen the Romulans as the Chinese of the Galaxy.