<sigh> this is the third time I've seen this come up on HN. Because for some people the word "slave" has bad connotations. Therefore it is a cultural norm in the USA not to use the word slave, even though as you say it has been in common usage in engineering (e.g. Master/Slave flip-flop going back to the 1950s). To use the word shows cultural insensitivity in some cultures.

Like you I had not come across this issue when I landed as a fresh immigrant in California in 1996 to work on replication, but it only took a few minutes for someone to explain it to me and we carried on saying "supplier/consumer" or "origin/destination" for the subsequent 2 decades without trouble..