TITLE: What is so "plactic" about the plactic monoid?
QUESTION [11 upvotes]: The plactic monoid is the monoid consisting of all words from the alphabet $\mathbb{Z}^+$ modulo certain relations. It is important mainly because its elements enumerate semistandard Young tableaux. 
I believe the plactic monoid was introduced by Knuth, but without that name. Lascoux and Schützenberger named it "le monoïde plaxique" in a French paper (1981) of the same name. (DISCLAIMER: I have never seen that paper; perhaps my second question is answered in it.)
Several questions: 
1) How did plaxique $\rightarrow$ plactic? (This isn't the most obvious Anglicization; note that the MathSciNet entry for the original Lascoux/Schützenberger paper translates the title as "Plaxic'' monoids.) Who introduced the latter form of the word and why?
2) What is plactic/plaxique supposed to mean? As far as I know neither was a word in their respective languages before being applied to the word monoid/monoïde. I am entertaining an etymology from Greek $\pi \lambda \alpha \xi$ "flat surface," but I don't find it very compelling.

REPLY [4 votes]: The English translation of Symmetric Functions, Schubert Polynomials and Degeneracy Loci by Laurent Manivel contains the following footnote on the phrase "plactic ring":

From the Greek $\pi \lambda \alpha \xi$, flat place, stone plate, tablet. This terminology is due to Lascoux and Sch\"utzenberger.

There is no evidence provided for this assertion, but the fact that the author is French makes me suspicious that he has insider information. There is no discussion of why this name was chosen or what it is meant to suggest.