Arachidonic acid, the double bonded fatty acid, is occasionally misrepresented as having to do with spiders (arachnids). The Wikipedia entry explains that it's instead elated to "arachis" = peanut in New Latin. Alas, peanut oil does not contain any of it. Bizarre! What went through the mind of the person who named this lipid and caused all the confusion and mispronunciation by learners? Is there any good reason for the name?

  • $\begingroup$ I’m voting to close this question because it is not about a problem in biology, but about the trivial name given to a compound over 100 years ago. It is little more than a rant, disguised as a question, the answer which can not possibly be known "what went through the mind…". $\endgroup$
    – David
    May 9, 2023 at 15:22

1 Answer 1


There are finitely many letters and possible combinations of them making words, and many many things to be named. Inevitably, some of the words will be similar or even homonyms. To me, having some really limited and basic knowledge of Latin and (Ancient) Greek, there is no real confusion here. All terms related to spiders have a different stem containing an n, namely arachnophobia arachnologist, Arachnida ...

Regarding the naming, it was suggested in 19131 based on its similarity to arachidic acid, which is indeed a (minor) constituent of peanut oil.

1 Martin, S. A. et al. The discovery and early structural studies of arachidonic acid. J Lipid Res. 2016

  • $\begingroup$ Thanks Domen. That's just the paper I was looking for. I'm citing here to document the answer for readers here: "The name, arachidonic, was suggested in 1913 based on its relationship to the well-known arachidic acid (C20:0). It took until 1940 before the positions of the four double bonds were defined at 5,8,11,14 of the 20-carbon chain." Arachidic acid seems to a minor constituent of peanut oil at around 1%. $\endgroup$
    – SeanJ
    May 11, 2023 at 8:35

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