My theory is that these voltages pre-date Edison and were chosen because of arc lamps, which were invented and marketed earlier than incandescent lamps. Three-phase and split-phase systems are usually based on one of these voltages, like the 127/220 V I mentioned. 277/480 V in the US also fits in (480/8=60) but might be a more recent invention, I don't know about that.
Split-phase is the term most commonly used in Europe for single-phase three-wire systems as used in the US. They've never been particularly common but some areas of Germany once had 110/220 V split-phase and the British Isles have 230/460 V supplies for remote rural locations like larger farms. Some central European railways also use split-phase for switch point heaters, at the extremely odd nominal voltage of 231/462 V at 16.7 Hz, derived from the 15 kV overhead wire. I suspect these systems might have been created in order to convert Edison DC supplies to AC without running additional cables. In the UK they were a cost-saving method because these remote places then only required single-phase medium voltage but that might not have been the original reason behind the system as such.
