linguistic (adj.) Look up linguistic at Dictionary.com
"of or pertaining to the study of language," 1824, from German linguistisch (1807); see linguist + -ic. The use of linguistic to mean "of or pertaining to language or languages" (1847) is "hardly justifiable etymologically," according to OED, but "has arisen because lingual suggests irrelevant associations." Related: Linguistical; linguistically.
To the science which may be formed by comparing languages, the term Linguistic has been applied by some German authors. It is not, however, generally adopted, and is liable to some objections. ["Biblical Repository," vol. vii, no. 21, Jan. 1836]