Who did first use the term "simple" in group sense and why? 
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*Who did first use the term "simple" in group sense? More appreciated if I learn the original word(might be in French, Galois???)...


and also... 


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*Why do you think that this term is chosen etymologically? A meaning of "ease"?(To me, sounds not plausible) Or, a sense of "being core/atom"?(Just a guess!)


P.S. This question might contribute a better perspective of simple groups for me and whoever reads here.

It seems that Galois was the first to talk about simple groups using these terms. The first page of A brief history of the classification of the finite simple groups by Solomon says:

Galois introduced the concept of a normal subgroup in 1832, and Camille Jordan in the preface to his Traité des substitutions et des équations algebriques in 1870 [J1] flagged Galois’ distinction between groupes simples and groupes composées as the most important dichotomy in the theory of permutation groups. 

