Dictionary of Medieval Names
from European Sources

Dagbert m. Old Saxon, Old Dutch dag, Old High German tag 'day' + Old High German beraht, Old Saxon berht 'bright' from Proto-Germanic *berhtaz.

The name of a number of 7th C Frankish kings.

Spellings such as Dambert developed from the lengthening of dag to dagin which was then shortened to dain.

France
Latin
628 Dagobercthus (nom) DCEL-2 CCXLV, Dagoberti (gen) ibid. CCXLIV; 629 Dagoberti (gen) ibid. CCXLVI, Dagobertus (nom) ibid. CCXLVI; 634 Dagoberti (gen) CartYonne1 IV, Dagoberto (abl) ibid. IV; 711 Dagoberti (gen) ibid. IX; 1031 Daibertus (nom) StVdM-II 684; 1147 Daimberti (gen) clairvaux-12thc 19, Dainbertus (nom) ibid. 19
Germany
Latin
634 Dagobertus (nom) UrkPreu-1 3; 1137 Dagoberti (gen) quix-vol1 102
Cite as: S.L. Uckelman. "Dagbert". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2016, no. 4. http://dmnes.org/2016/4/name/Dagbert.