What is the meaning of D-?

deci- (×10)

deprecated notation for dextrorotatory (versus modern notation, (+)).

my

him

it

Alternative form of dh-

Alternative form of il-

the d- classifier or valence-change prefix, a detransitivizing prefix of active verbs that modifies the transitivity or valence and grammatical voice of a verb, occurs in most passive, mediopassive, reflexive, and reciprocal verbs that are derived from verbs with a ∅- classifier; it produces the agentive passive verb forms

Source: wiktionary.org