Downvoters, please explain your downvote.

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That's my reason for the downvote; it seems to me to be very odd to keep asking the same question - and even answering it yourself - again and again. If you don't have an agenda, maybe you can explain? Also, look at your second Ngram: embryectomy has never been a "popular" term for the treatment of ectopic pregnancies, not even when Steadman gave that definition. What I notice from that Ngram is a blip indicating it was in use mostly in the 50's-70's, when abortion was becoming decriminalized. I suspect the term was used mostly by laypeople with an agenda.

@anongoodnurse But embryectomy ≠ induced abortion (embryotomy, yes). The reason I keep asking this question is that embryectomy is a precise term, so why has it fallen into disuse?

Actually, I'm thinking of revising my answer to say it was never used by medical professionals. The usage appears to have been almost entirely by non-medical people except a few rare papers involving animal studies.

@CareyGregory - Exactly. To my knowledge, the term was never embraced by the medical profession.

@anongoodnurse But "embryectomy" appeared in Stedman, Practical Medical Dictionary (1916), p. 302 that I quoted

@anongoodnurse Or the 2002 Springer Lexikon Pflege (Springer Encyclopedia of Nursing), also quoted in my question.

@Geremia - Have you thought about anything anyone here has told you? I believe embryectomy is a proper term for animal experiments where embryos are removed for research purposes. But Google Scholar (which goes back a long time as well) doesn't have any paper with "embryectomy" referring to a human, because investigators aren't in the habit of taking babies out of mothers at various stages of development for study. Why do you insist that it is a term that was in use by physicians? Lexikon Pflege doesn't sound English. Maybe it's used in other countries? But not in the US.

@anongoodnurse "Why do you insist that it is a term that was in use by physicians?" Because it appears in a 1916 and 2002 medical dictionaries. Springer Lexikon Pflege's entry "Embryektomie" cross-references the English word "embryectomy". "I believe embryectomy is a proper term for animal experiments where embryos are removed for research purposes." That could be, but my question remains: What is the treatment of an ectopic pregnancy called?

Physicians have a responsibility to keep up with the pertinent literature, which may include animal studies for some. I doubt it's a difficult word to understand, but maybe Steadman's included it for that reason. To illustrate your other argument, gebärmutterhalskrebs is in Lexikon Pflege, but its usage among English speaking doctors certainly didn't "fall out of favor". Language is a strange and mutable thing; there are a lot of words in the dictionary that most people don't use.

@anongoodnurse and Geremia - FYI, I rewrote my answer.

I think you would call the surgical procedure of removing ectopic mass just a laparoscopy. At least this is what I could find in the NICE guidelines (UK). I could not find the German term (Embryektomie) in the German equivalent of UpToDate and have never come across it. Also, how would you call the procedure after week 10? Fetectomy since the embryo has then reached fetal stage and should be called a foetus? Gebärmutterhalskrebs is the German term

for cervical cancer (literally: Gebärmutterhals = uterine neck = cervix and Krebs = cancer), so I‘m not quite sure where that argument came from (from either side @anongoodnurse and @Geremia)

@Narusan - salpinghectomy/ectomy, oopherectomy and laparoscopy/otomy were all given to the OP in a previous response. They wanted a generic term that covered every situation. I know what gebärmutterhalskrebs means, My point is it doen't matter what words other languages use for something.

@Narusan - Also, in the US at least, laparoscopy is just a procedure. It given no clue as to what was done except that something surgical was done in the abdomen with a laparoscope.. It could be anything from a tubal ligation to an appendectomy.