EVO ŠTA KAŽE WIKI
Various etymologies for Latin Germani are possible. As an adjective, germani is simply the plural of the adjective germanus (from germen, "seed" or "offshoot"), which has the sense of "related" or "kindred" or "authentic". According to Strabo, the Romans introduced the name Germani, because the Germanic tribes were the authentic Celts (γνησίους Γαλάτας; gnēsíous Galátas). Alternatively, it may refer from this use based on Roman experience of the Germanic tribes as allies of the Celts.
Sad zašto bi Rimljani zvali Germane autentičnim keltima