"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]
*dnghū-, Proto-Indo-European root meaning "tongue."
It is the hypothetical source of/evidence for its existence is provided by: Latin lingua "tongue, speech, language" (from Old Latin dingua); Old Irish tenge, Welsh tafod, Lithuanian liežuvis, Old Church Slavonic jezyku "tongue;" Old English tunge "tongue; speech."
in reference to a group of related North American native languages, 1915, coined by U.S. anthropologist and linguist Edward Sapir from *-ne, a stem in the languages for "person, people," and Athabaskan Dene "person, people." "The compound term Na-dene thus designates by means of native stems the speakers of the three languages concerned, besides continuing the use of the old term Dene for the Athabaskan branch of the stock" [Sapir].
"smallest meaningful unit in a language," 1896 (but originally in a different sense, "root, suffix, prefix, etc."), from German morpheme, coined 1895 by Polish-born linguist Jan Baudouin de Courtenay (1845-1929), from Greek morphē "form, shape," a word of uncertain etymology, on analogy of phonème.