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Magma is one of those beautiful words of Greek origin (μάγμα) that arouses the child and the wild in me, making me think of volcanoes. I just found out, though, that it is also used in mathematics to mean a type of algebraic structure (a set paired with a binary operation on it)! I am very curious how this name was picked for this particular algebraic structure (which is also called by groupoid). Wikipedia attributes the coining of this term to Nicolas Bourbaki, but does not mention how they arrived at such a name. I have not been able to find the specific etymology of this sense anywhere else. What is its origin?

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Some coinages have no 'how' or 'why' beyond the idiosyncratic artful randomness of the individual author. There is surely some answer in the Bourbaki exegesis, but any such explanation would be idle speculation even on the coiner's part. How do we know what they were thinking when they made it up? Why 'group', 'ring', or 'field'? This might better be asked in math.SE as a history question. –  Mitch Apr 4 '12 at 13:27
@Mitch In the case of those other algebraic structures, they make some sense: a group is a set and a binary operation put together in a certain way...okay, I can see that. Etc. –  Kazark Apr 4 '12 at 13:37
so the word 'group' tells you intuitively that it is a binary operation, with identity and inverse? or that a field is a commutative ring whose multiplication is commutative over non-zeroes? Most likely not. Anyway, your initial explanation, though fanciful, is probably on target for the original justification (modulo the arbitrariness). –  Mitch Apr 4 '12 at 13:45
"Mathematicians are like Frenchmen: whatever you say to them they translate into their own language, and forthwith it is something entirely different." -- Johann Wolfgang von Goethe (1829) –  John Lawler Apr 4 '12 at 15:29
Amazing how Goethe used fancy words like "forthwith"! –  GEdgar Apr 4 '12 at 21:08

2 Answers 2

up vote 10 down vote accepted

It may be a pun. Looking up magma in the French wikipedia*, another name for magma in French is groupoïde de Ore. Here Ore is a Norwegian mathematician, but ore in English is mineral-bearing rock, whereas magma (in both English and French) is molten rock.

Would Bourbaki have based a mathematical term on this pun? I'm not in a good position to judge; maybe somebody else could comment on this.

* Since Bourbaki was a pen name used by a group of French mathematicians, this is the right language to search in.
There is also a groupoïde de Brandt, also called a groupoid in English, which would explain why Bourbaki felt compelled to coin a new name.

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Note: this answer was invented by Peter Shor. –  GEdgar Apr 28 '12 at 23:49

Wikipedia says (without reference)

In French, the word "magma" has multiple common meanings, one of them being "jumble". It is likely that the French Bourbaki group referred to sets with well-defined binary operations as magmas with the "jumble" definition in mind.

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Larousse says the figurative definition of magma is Mélange confus, inextricable de choses abstraites and gives the example usage "Ces propositions constituent un magma incohérent." Looking at some instances of its use, I would say the English definition would be something like confusing, inseparable, and worthless jumble; this isn't a bad name for the algebraic structure, although possibly the pun from my answer may have also influenced Bourbaki's choice of name. –  Peter Shor Apr 5 '12 at 15:24

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