Most books say, that the second part of the name is what is now “Not” in modern
German, then meaning “danger” (in battle) or “eagerness”. But in a usually quite reliable book (
Rosa und
Volker Kohlheim, Das große Vornamenlexikon, Mannheim 2003) I found, that the -NOT part is from a word meaning “fight”, that goes back to Old West Nordic “hniótha” (to strike). Does anybody know more?
Satu maybe?