I don't know the underlying science to which I refer when I talk about a PC sync terminal connection between camera & electronic flash. What's the meaning of the letters "P" & "C" in PC sync terminal?
It stands for "Prontor-Compur connection":
"Prontor" has its origins in the Italian word "pronto", meaning ready (and was a leaf shutter made by Alfred Gauthier). "Compur" is derived from the word "compound" (the "Compound" was a long-lived series of leaf shutters made by Friedrich Deckel).