A tree from FMC Technologies
There are large metal things installed in oil fields at the bottom of the ocean called Christmas trees, or just trees for short. The name came about, I’m told, because someone thought these rectangular metal objects looked more like a Christmas tree than some large industrial equipment.
My best guess is that, after the equipment was designed and then built under some other name, various people came to look at the first unit in the building where manufacturing had just finished. One guy was wearing glasses with really thick lenses from an old and outdated prescription. So old, in fact, that the lenses were scratched all over. He wasn’t legally allowed to drive because of his vision. This guy looked at the unit with a corner of the building behind the it. At this corner were some towering containers, above which was a light. The light cast a shadow down the corner, but illuminated the walls to either side, making a triangular dark region behind the unit. With help from the lights on the unit and the scratched lenses, the unit seemed to have twinkling lights.
So the guy exclaims that it looks like a Christmas tree, and everyone else tries to hide their laughter. They go along with the name because it is just too ridiculous. Later, they call it a Christmas tree to make fun of the guy, and it becomes an inside joke. But, it is a catchier name than whatever they were using before, so they find themselves calling it a Christmas tree even when they don’t mean to joke. The name sticks.
That isn’t really how it happened, but I think it is a much funnier version of reality.