From the Historical Grammar of Iranian Languages

Contrary to claims in standard grammars that Iranian past passive participles in -ta- & -na- are formed from simplex roots, examples are adduced of participles of this type derived from stems obtained by root reduplication; some of the roots in question are obscured by loss of a root consonant. For the first time, the Kurdish preverbal particle d-, which confers a meaning of duration or repetition on a finite verb, is derived from the temporal adverb dvita 'always, constantly'; an originally wider meaning of this adverb, which once included 'from the beginning', is argued to be preserved in the first element of Old Persian duvitaparanam 'from time immemorial, of yore', a compound of two adverbs. References. Adapted from the source document