Gunni is a short form of a Norse masculine name containing gunn- (war).
Gonni [Sir Henry Ellis 1833 A General Introduction to Domesday Book 2: 130].
Gun’ [Sir Henry Ellis 1833 A General Introduction to Domesday Book 2: 135].
Gunni [Sir Henry Ellis 1833 A General Introduction to Domesday Book 2: 136].
Gunn- = battle [Gillian Jensen 1968 Scandinavian Personal Names in Lincolnshire and Yorkshire, page 344].
“Short forms of names in Class A formed by the addition of the suffixes -i (masc.) or -a (fem.) to one or other of the elements” [Gillian Jensen 1968 Scandinavian Personal Names in Lincolnshire and Yorkshire, page xxxi].
“Gunni m. PN. koseform zu namen, zusammengesetzt mit gunnr” [Jan de Vries 1962 Altnordisches Etymologisches Wörterbuch, 2nd edition, page 195].
A man called Gunni held land in Somerset in the time of King Eadweard III (the Confessor): “Gunni teneᵬ T . R . E . ⁊ geldᵬ ᵱ . ɪɪɪ . hiᵭ ⁊ dim͛” [Caroline Thorn & Frank Thorn 1980 Domesday Book 8 (Somerset): chapter 29, paragraph 1]: “Gunni held it TRE and it paid geld for 3½ hides” [Ann Williams & Geoffrey Martin 2002 Domesday Book 1: 267].