[noggin]

Originally YUV was introduced with color television as a means of having a signal that was compatible with both black/white and color TVs. But the term YUV does not refer to this specific implementation (instead we simply use "PAL") but as the equivalent of "component", which again is the equivalent of either/both YCrCb/YPrPb (and they are also used interchangeably even though they normally are seperated in the analog /digital domans)

I think YUV was particularly introduced to define the U & V colour difference signals within a PAL encoder/decoder - with NTSC using the different YIQ system with I & Q colour difference signals which were phase rotated by around 33 degrees to optimise the asymmetric bandwidths that NTSC encoders theoretically offered. I & Q were phase rotated to encode the colour differences the eye was more sensitive to in the higher bandwidth channel. However in reality I don't think the bandwidth differences were exploited because of the differential delay that the two different filters would have introduced (and would have required compensation for) I believe SECAM also used a different representation - YDbDr - as it used different weightings (and line alternate chroma)

YUV/YIQ was not used to describe the resulting analogue composite/coded (composite was also used to describe B&W video signals as it defined a video signal with integrated, rather than separate, sync pulses) video signal - just the original component representation used during encoding (usually from RGB analogue - either in the camera head or CCU, or sometimes downstream)

YUV has often been used as shorthand for YCrCb since (particularly in PC video) - but I think technically it is quite tied up with PAL encoding.

YPrPb analogue component was always a bit trickier. ISTR that there were multiple analogue level standards for component analogue video when it was first introduced, which was around the time Betacam and Betacam SP VTRs and camcorders arrived. There were definitely two options for analogue component level output on Beta SP VTRs - one of which was an EBU (European Broadcasting Union) standard, but I'm not sure what the other one was. (Off topic now - sorry)