Any tales I've ever heard of "the witching hour" have to do with the belief that approximately 3a.m. is the time when all the spooks, witches, demons & other creepy creatures come out from their respective dwellings and hiding places to do their dastardly deeds. It's the hour when it is most dangerous and frightening and leaves the innocent public at risk of being preyed upon.
Many decades ago it was considered to be Midnight, but somewhere along the way, I guess these nasty shadowy figures decided to change the hour to 3 a.m.
Of course this is all myth and/or folklore that has no meaning in reality. However, there is the belief that "Nothing good ever happens after Midnight."......which IMO was fabricated by parents of teen-agers or wives with husbands who went out with the guys too often! It's all part of the "Spook & Guilt Method" of control!..............Paula