"of the same parents or grandparents," c. 1300, from Old French germain "own, full; born of the same mother and father; closely related" (12c.), from Latin germanus "full, own (of brothers and sisters); one's own brother; genuine, real, actual, true," related to germen (genitive germinis) "sprout, bud," of uncertain origin; perhaps a dissimilation of PIE *gen(e)-men-, suffixed form of root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups.
Your cousin-german (also first cousin) is the son or daughter of an uncle or aunt; your children and your first cousin's are second cousins to one another; to you, your first cousin's children are first cousins once removed.
Þe empere passede from þe Grees to þe Frenschemen and to þe Germans, þat beeþ Almayns. [John of Trevisa, translation of Higdon's "Polychronicon," 1387]Their name for themselves, die Deutschen (see Dutch), dates from 12c. Roman writers also used Teutoni as a German tribal name, and writers in Latin after about 875 commonly refer to the German language as teutonicus (see Teutonic). Meaning "the German language" in English is from 1748. High German (1823 in English) and Low German as a division of dialects is geographical: High German (from 16c. established as the literary language) was the German spoken in the upland regions in southern Germany, Low German (often including Dutch, Frisian, Flemish), also called Plattdeutsch was spoken in the regions near the North Sea. In the U.S. German also was used of descendants of settlers from Germany.