Around 1600 before the year 0 they lived in South-Scandinavia, Denmark and Northern-Germany. Around the year 0 they expanded until the Rhine, Weichsel and Donau. They repressed there with the related Celtic people or mixed with them. How the Germanic people called themselves is unknown.
The word Germaan (German or Germanic in English), of which the etymology is uncertain, might have arisen from ger (=spear) and man (=man, hero). There has also been said there might be some coherence with Herman (=man from the army). I translated to Army in reference to heir – the Dutch word would’ve been leger.
The Latin word Germanus can mean “brothers and sisters of the same parents”. The name could’ve originated from the expression “germani Celtarum”, so the relatives or “brothers” of the Celts. The difference between the Celtic and Germanic people has only been made since the Romans came into the Northern lands.
Finally, it could be that germani is derived from grimani that could mean “screamers/yellers” and is related to our word “grimas” and the Latin word for mask: In battle the Germanic people started a frightening battle-cry with painted faces.
So much on the origins of the word “German, Germaan, Germanic”.
More on this topic, another time!