"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]
in the names of sciences or disciplines (acoustics, aerobics, economics, etc.), a 16c. revival of the classical custom of using the neuter plural of adjectives with Greek -ikos "pertaining to" (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their English names before c. 1500, however, tend to be singular in form (arithmetic, logic, magic, music, rhetoric). The grammatical number of words in -ics (mathematics is/mathematics are) is a confused question.