[Blubatt]

The simplest description for the channel names is that they were all launched at different times, likely launched with different creative visions, and different creative people at the helm. A channel like BBC America, which launched in 1998, is going to have a legacy brand name, compared to BBC First, which launched in 2014. To be fair, the channels are slowly coming into line. BBC HD, BBC Entertainment are being replaced with BBC First, BBC Earth, and BBC Brit in the countries which have the former. Its likely that BBC America, one day, will be superseded by BBC First, like in Canada.

As for the programming, its just about what each channel has rights to, nothing special about that.