On a typewriter from around the time of the first Macs, the return key normally moves back to the beginning and moves down a line, so that's probably why they picked it. They also called the key "return" rather than "enter."
On a classic non-electric typewriter the carriage was returned by pushing a lever on the right side of the carriage. The lever could be pressed to the left relative to the carriage which would move the paper up. At the end of travel relative to the carriage if you kept pushing it would move the carriage back to the left. Hence CR and LF could be accomplished in one motion. If you wanted to advance the paper many lines, you'd push the lever multiple times - probably with the carriage all the way to the left the whole time.
On another note, I find it incredibly weird describing an "everyday" item like a typewriter because many people on HN may have never used one!
It's a simple mechanical artefact. Carriage return moves the paper carriage all the way to the right (returning it to its initial position), while line feed will advance the paper vertically (feeding a line through the carriage). With that in mind, line feed and carriage return on their own make about as little sense.
On later type writers both the line feed and carriage return were integrated into a single key or lever, which was just called carriage return or return. From this perspective, an encoding using a lone CR for newlines might make more sense than one using a lone LF. But neither combination really makes intuitive sense in buffered, electronic systems. It's just how it is.
Somehow the friends who told me how to use a PC always used "Return" instead of "Enter", but this was in Germany where we didn't have any text on this key, just a big arrow pointing down and left.
