Arnegundis was sister of Ingonde, third wife of Clothar. Gregory of Tours makes it clear that the marriage was polygamous as he records that Clotaire reported his "marriage" to Aregonde to his wife Ingonde. She is named "Chæregundem" in the Liber Historiæ Francorum. 1
Arégonde married Chlothachar I "le Vieux" MEROVING King of the Franks in Soissons, son of Chlodovech (Clovis) I "The Great" MEROVING King of the Salian Franks and St. Chrotechildis GJÚKUNGAR Princess of Burgundy. (Chlothachar I "le Vieux" MEROVING King of the Franks in Soissons was born about 502 in Rheims, Marne, France and died on 23 Nov 561 in Compiègne, Oise, France.)
Foundation for Medieval Genealogy, http://fmg.ac/Projects/MedLands/MEROVINGIANS.htm#_ftnref162.