An Etymological Dictionary of the German Language/dann

by Friedrich Kluge

dann, adv., from the equiv. MidHG. and OHG. danne, ‘then, at that time, in such a case, thereupon’; properly identical with denn; in MidHG. and OHG. danne is used indifferently for denn and dann. AS. þonne, þœnne, E. then. The OTeut. adv. is based on the pronominal stem þa- (comp. der); yet the mode of its formation is nor quite clear. Comp. da, der, and the following word.