For IDE you are mixing up 2 separate concepts. The addressing primary/secondary is purely addressing, I don't recall seeing "Master/Slave" in relation to that. Labeling on HDDs I've seen always used primary/secondary
Where the master terminology comes in is that a certain version of ATA added bus mastering DMA from the drive. Maybe some harddisks had a jumper to disable or enable that
This is verifiably untrue. Older IDE hard drives commonly used master and slave on their printed labels instead of primary and secondary. Google “ide drive master slave” images and you’ll see plenty of examples.
I don’t say this to justify sticking with the older terms, just to assert that they were actually used.
There is a double confusion here because "primary" and "secondary" were used to refer to IDE channels. Most machines had two IDE channels (i.e. physical connectors on the controller card), each of which could have a master and slave device (two connectors on the cable).
So you have IDE0, primary, and IDE1, secondary. For the four devices a typical system would support, they would be referred to as primary master, primary slave, secondary master and secondary slave. This was extremely accepted terminology.
Newer machines and BIOSes could usually boot from any of these four devices but originally, many machines could only boot the primary master. That's why it's the master and the other one is the slave -- it is subservient in the sense that it can not be a boot drive and was usually used for secondary storage, not OS.
Where the master terminology comes in is that a certain version of ATA added bus mastering DMA from the drive. Maybe some harddisks had a jumper to disable or enable that