"a German," 1833, in modern use often in contrast to Celt, probably a back-formation from Teutonic.
Entries linking to Teuton
Used in English in anthropology to avoid the modern political association of German; but in this anthropological sense French uses germanique and German uses germanisch, because neither uses its form of German for the narrower national meaning (compare French allemand, for which see Alemanni; and German deutsch, under Dutch). In Finnish, Germany is Saksa "Land of the Saxons."
The Teutonic Knights (founded c.1191) were a military order of German knights formed for service in the Holy Land, but who later crusaded in then-pagan Prussia and Lithuania. The Teutonic cross (1882) was the badge of the order.
It is the hypothetical source of/evidence for its existence is provided by: Old Irish tuoth "people," Old Lithuanian tauta "people," Old Prussian tauto "country," Oscan touto "community," German Deutsch, Gothic þiuda, Old English þeod "people, race, nation," Old English þeodisc "belonging to the people." But Boutkan says it is probably a substratum word.