Sunday

late 14c., ethimolegia "facts of the origin and development of a word," 
from O.Fr. et(h)imologie (14c., Mod.Fr. étymologie), from L. etymologia
from Gk. etymologia, properly "study of the true sense (of a word)," 
from etymon "true sense" (neut. of etymos "true, real, actual," related to eteos "true") + -logia 

"study of, a speaking of" (see -logy). In classical times, of meanings; later, of histories. 
Latinized by Cicero as veriloquium
As a branch of linguistic science, from 1640s. 
Related: Etymological; etymologically.