Belonging to how a thing actually works. Of the layer that must be right whether or not anyone sees it.
Greek τέχνη (techne, art, craft, skill), via Latin technicus; what belongs to how a thing actually works takes its name from craft rather than from theory, and must be right whether or not anyone sees it.
What sits underneath appearance, holding the actual machinery together. Correctness here is owed to the thing itself, never to whoever happens to be watching.