Reconstruction:Proto-Indo-European/-dʰrom

Alternative forms
, ,

Etymology
Variant of.

Sometimes hypothesized to have developed from assimilation to a preceding voiced aspirate (compare Bartholomae's law in Indo-Iranian). Sihler describes this as the usual explanation and considers it "the only remotely plausible" one if the *t- forms of the suffix are original, but says it is problematic, noting that this form of the suffix is not attested in contexts like Greek (from ) even though, under this hypothesis, the *-dʰ-initial variants would have originated in words like this.

Based on the contexts in which it occurs, Olsen 1988 argues that it actually originated from coalescence of a voiceless laryngeal (*h₁ or *h₂) with the following *-t-, initially resulting in a voiceless aspirate, which is proposed to have merged with the outcome of voiced aspirates in the languages in which this allomorph is attested.