Did my teacher make this etymology for もしもし up?

Question

I was reading this question, and realized that I had been told something outlandishly different. To be clear, what I was told didn't change the usage of もしもし to be something different.

I was told that the phrase comes from an interesting story. One of my teachers claimed that もしもし is a phrase that Japanese people believed monsters could not say. Therefore, to confirm that the other person on the phone (including door intercoms, etc.) is not a monster (赤鬼とかね), and that they are indeed human.

To my naive mind, this made a lot of sense, and it explained why もしもし is used the way it is. Now, looking back, I'm inclined to disbelieve this claim. It just doesn't fit with the other articles I have read on the subject.

So did my teacher make up the story, or is this a real thing?

Answer 1

He may have read a story similar to this one: https://www.tofugu.com/japanese/moshi-moshi/ (See "Foxes" Section on that page)

Excerpt: "The explanation that seems the most plausible because it's actually supported by facts. On 12/16/1890, phones were 1st introduced to 日本. At the time, only rich people were were able to afford telephones. Being rich, they were used to talking down to others. Thus, the standard "telephone hello" was おいおい or "hey YOU!" The person on the other end would respond with はい、良うございます or はい、良うござんす. Both of these are humble ways of saying, "Yes, I'm ready" meaning the person calling is ready to talk.

Of course, this abrupt "hey YOU!" got on people's nerves when telephone operators used it. So the "oi oi" was changed to 申し上げます.

"Moushiagemasu" was eventually shortened to 申す申す for male operators and 申し申し for female operators. Some male operators still used "oi oi" for a while though.

The person who made the change to "mousu mousu" or "moushi moushi" on the telephone was Shigenori Katougi (加藤木重教). He was an electrician for the Ministry of Engineering and went on to work for anaka Seisakusho (田中製作所). He traveled the US in 1889 to study their phone system.

During his visit, Katougi-san learned Americans say "hello" when answering the phone. Katougi's American hosts asked what the telephone greeting was in Japan. He wasn't sure what to tell them. It was either "oi oi," "moushiagemasu," "mousu mousu," or "moushi moushi." It would have required a lot of explanation (about as much as this article). So he just decided to tell the Americans that Japanese people say "moshi moshi" and it means "hello."

This gave him the idea of a standardized "telephone hello" which he brought back to Japan. Soon after in 1893, the term "mousu mousu" was shortened to "mosu mosu" and "moushi moushi" was shortened "moshi moshi."

But after a while there were fewer male telephone operators than female. So "もすもす" eventually disappeared and "もしもし" became the standard. Historians say this happened in 1902, and both men and women used "もしもし" after that."

Answer 2

This may be a well-known folktale, but it isn't the real etymology at all (and sounds much more like a folk etymology than a real one anyway).

もしもし is a contraction of 「申し、申し」, i.e. 'speaking, speaking', said as a way to confirm to the caller that their call had connected. The particular word 申す was chosen to avoid any accidental impoliteness caused by not using a formal enough word.

Source: http://gogen-allguide.com/mo/moshimoshi.html