The quicio of a door is basically the part where it joins the frame:
- m. Parte de las puertas o ventanas en que entra el espigón del quicial, y en que se mueve y gira.
It is used figuratively in expressions like "sacar de quicio", meaning "to exasperate, to take on somebody's nerves".
But the DLE entry does not include the origin of the word ("from Lat. quicium" or something like that), so...
What is the origin / etymology of quicio?