From Wiktionary, the free dictionary
From maðr + -gi.
manngi (genitive mannskis)
- no man
...á þeim meiði er manngi veit...- ...from that gallows-tree that no one knows...
- (Hávamál 138)
- Zoëga, Geir T. (1910) “manngi”, in A Concise Dictionary of Old Icelandic, Oxford: Clarendon Press; also available at the Internet Archive