E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Cousin-german.
The children of brothers and sisters, first cousins; kinsfolk. (Latin, germanus, a brother, one of the same stock.)
1
There is three cozen-germans that has cozened all the hosts of Reading, of Maiden-head, of Colebrook, of horses and money.Shakespeare: Merry Wives of Windsor, iv. 5.