The name
We took the name cerne — heartwood — for the part of a tree you cannot see, and which holds up the rest. It is what these businesses are in the buildings they work in.
The part you do not see
Heartwood is the wood in the middle of the trunk. It was the first ring the tree made, and after a few years it stopped growing and stopped carrying the sap. Everything in the tree that is alive and growing has moved outside it. And yet it is the heartwood that takes the weight: it is the densest and the darkest part, the part that does not rot, the part that keeps the trunk from bending in the wind. None of it is visible from the outside. Only when the tree comes down does what was holding it up come into view.
What these companies are
This is exactly what an HVAC, electrical or plumbing company is inside a building. All of it sits behind the walls, above the false ceilings and down in the basement. The people who work in the building every day do not know the name of whoever installed it or of whoever maintains it, and that is the sign it was done well. The work is noticed on the day it fails: when an operating theatre loses its air conditioning, when a hotel in August has no hot water, when a factory stops because there is no power. The rest of the year the building works and nobody thinks about it. It is work that holds up everything around it without being seen, and that is why we gave the group the name a tree gives to that part of itself.