I've been designing/building digital electronics, and programming computers, for 40 years. However it wasn't until I started pondering the three locks in series, in this photo, that I realized the the use of the term "gate" for the building-blocks of digital circuitry was more than a metaphor.
This literally is an OR gate. If any one-or-more of the locks is unlocked, the whole gate is unlocked. An AND gate could be implemented by putting the locks in parallel (over the same pair of links); every lock would need to be unlocked before the gate would open.