Admittedly the name is poor, but memccpy has been in POSIX since forever (the opengroup.org manual mentions it's from "Issue 1" which I believe refers to the X/

Admittedly the name is poor, but memccpy has been in POSIX since forever (the opengroup.org manual mentions it's from "Issue 1" which I believe refers to the X/Open Issue 1 from 1985), so I guess the C committee thought that an existing poor name was better than coming up with a new one.