Baud rate is the maximum number of transitions per second of the state of a transmission medium. Hz is the actual number of cycles per second, so it varies degending on the data transmitted. Bitrate is the number of bits transmitted per second.

Usually bits are transmitted in groups with some redundancy to allow errors to be corrected. E.g. early Ethernet used 8b/10b encoding; 8 bits of data were transmitted as a 10 bit "symbol".

With a 1b/1b encoding baud rate would equal bit rate, but in practice that was essentially never used so the numbers woud diverge. Bitrate is more meaningful to the user.

SI and binary prefixes can be applied to baud, so kilobaud is certainly a word.

It may have been misused at some point, but "baud" was a word long before the internet, and I distinctly remember my modem at the time using the word baud on the box. I was just a teenager, so I'm sure I was missing key information. It was used, tho.

Here, this is proving us both right:

If your modem-to-modem connection is at 14400 bps, it's going to be sending 6 bits per signal transition (or symbol) at 2400 baud. A speed of 28800 bps is obtained by 3200 baud at 9 bits/baud. When people misuse the word baud, they may mean the modem speed (such as 33.6k).

Kilobaud is definitely a word that means a thing. Baud is a literal unit of measure that uses the metric prefixes.

¯\_(ツ)_/¯