Schrödinger wrote a letter to Einstein after the 1935 EPR paper, and in that letter Schrödinger used the German word "Verschränkung" which translates into "entanglement", but when was the word first used in English?

Schrödinger's 1935 paper written in English, called Discussion of Probability Relations between Separated Systems, says (according to Wikipedia) "I would not call [entanglement] one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought" which means the concept was there but it whatever word he used for it was not entanglement (hence the square brackets). Unfortunately I do not have access to the full paper.

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    Matthias Christandl researched this at some point, going as far as a trip to the Schrödinger archive, just to resolve a bet with Artur Ekert. I don’t remember what conclusion he came to, but that might help focus your search. – DaftWullie May 19 at 5:49
up vote 6 down vote accepted

I managed to get access to the paper mentioned in the question. Schrödinger in 1935 (the same year the original EPR paper was published) wrote in English: "By the interaction the two representatives (or $\psi$-functions) have become entangled." This was in the abstract.

He also wrote later in the paper: "What constitutes the entanglement is that $\psi$ is not a product of a function of x and a function of y."

He also used the term "disentanglement"

However the use of the term as found by searching: quantum entanglement
in Google Scholar indicates that the term was merely doubling every 10 years until roughly 1990 when it went up by a factor of 5 in a 10-year period, followed by further factor of 6 in the next 10-year period:

enter image description here

Data was collected just now:

1900-1940: 63 results
1900-1950: 93 results
1900-1960: 146 results
1900-1970: 313 results
1900-1980: 718 results
1900-1990: 1700 results
1900-2000: 9380 results
1900-2010: 61700 results
1900-2020: 151000 results

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    Great answer. Is the original freely available online anywhere to your knowledge? – DukeZhou May 23 at 18:50
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    Unfortunately I was not able to access it until I got on my university account. – user1271772 May 23 at 23:45
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    if i was going to start a pirates bay (don't worry, i'm not;) it would be for research papers and reference materials – DukeZhou May 24 at 19:09
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    There are some, which I won't mention here, you can check, but it's not going to be as easy to find as music or movies. The demand for a 1935 paper by Schroedinger is extremely niche. – user1271772 May 24 at 19:14

This is a soft answer, offered b/c I'm interested in the etymologies of terms we use in math and science. For what it's worth:

entanglement (n.) 1630s, "that which entangles," from entangle + -ment. From 1680s as "act of entangling." Foreign entanglements does not appear as such in Washington's Farewell Address (1796), though he warns against them. The phrase is found in William Coxe's 1798 memoirs of Sir Robert Walpole.
SOURCE: Online Etymological Dictionary

from:

tangle (n.) 1610s, "a tangled condition, a snarl of threads," from tangle (v.).
SOURCE: Online Etymological Dictionary

I make this connection because the idea of determinacy and strings/threads goes back to at least the ancient Greek Moirai (the Fates).

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    Interesting that "entanglement" came roughly 20 years after "tangle" – user1271772 May 23 at 23:44
  • @user1271772 and also that the word came through the Scandinavian languages where the Norns are the analog of the Greek Fates. (I'm inclined to believe the primary meaning of Norns as "entwiners" is the most reasonable assumption.) I'm seeing Verschränkung being used in exactly the same sense, although I haven't found a common root. – DukeZhou May 24 at 19:20
  • Meanwhile, this is interesting but I don't see anyone replacing "entanglement" with "implexion", (especially now that we have the Free Will Theorem, which reinforces the resonance of the terms in use;) – DukeZhou May 24 at 19:23

According to Matthias Christandl (who did some research on this to resolve a bet with Artur Ekert), while the term "entanglement" was first used in 1935, as already relayed in other answers, the concept was discussed by Schrodinger in 1932. This set of slides (slides 3-8 in particular) from a talk reproduce part of a document that details this. The full image is also on the front of his thesis.

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