What does Herman mean?
From Germanic 'heri' (army) and 'man' (man), giving 'man of the army, soldier'. The Latinized Arminius refers to the same Cheruscan war-leader.
What does Reginald mean?
From Germanic 'ragin' ('counsel, advice') + 'wald' ('rule, power'), i.e. 'ruler by counsel' / 'counsel-power'. Note: this is 'ruler/power', NOT literally 'king'. Reynold and Ronald are closely related forms.