A byte has been synonymous with an octet for as long as I can remember. I found a Wikipedia article [1] that describes the transition of a byte meaning the number of bits to encode character of text to an octet.
https://en.wikipedia.org/wiki/8b/10b_encoding
A byte is also referred to the smallest addressable unit. Which in most cases is 8 bits but many (I guess mostly niche architectures) have much larger characters/bytes, and is still very much relevant.