Mannus is considered the "First German King". Or the First Noble King among men. In 1ad Tacitus wrote that Mannus was the son of Tuisto (Tyr?) and the progenitor of the three Germanic tribes Ingaevones, Herminones and Istvaeones that later split to form all of the Germanic tribes across the north from Scandinavia to England etc.
A being with the same name etymologically appears in the Vedic traditions brought to India 4/5000+ years ago by our European Aryan ancestors. मनु (Manu) is the progenitor and first man to worship the Gods. The Sanskirt word for human मानव ( mānava) means "Children of Manu". The English word 'man' comes from the same source. It's such a shame that so many of our ancient European ancestors went to India, Iran and other far off places (4/5000 yrs+ ago). Little of them remains there now other than remnants of our ancient European Aryan traditions that we gave them.
Fortunately, some of our Aryan ancestors chose wisely and migrated throughout our native Europe completely dominating it rather than going south across the med etc. It's always better to stick with your own folk.
