>The 1961 patent for TTL never mentions 5 volts; it only specifies a “B+”, which seems like a term held over from the vacuum tube days. Source: U.S. Patent 3283170A.

Yes, the high-voltage B+ which served the same purpose from a vacuum tube power supply was soon eclipsed by the VCC or VCC+ nomenclature.

And B+ actually originated from battery powered radios before electronic power supplies were common.

The low voltage high-current "A" battery was connected to the filaments of the tubes to provide the heating, then the high-voltage "B" battery was connected to the main B+ point in the circuit to power the analog functions.

Both batteries may or may not be connected to each other or a common ground.

For tube equipment power transformers, the low voltage and high voltage are obtained from separate windings so they could basically be employed offering the same kind of wiring options.

For equipment requiring a negative supply voltage in addition, a third "C" battery would be hooked up with its positive terminal to ground. Then a third winding on an appropriate power transformer could substitute for this but that was referred to as B-.