'middle voice' or 'reflexive', and *n- 'passive'; the prefixes appear with various related meanings in the individual daughter languages and branches.
mˈɪdəl vˈɔɪs ɔːɹ ɹᵻflˈɛksɪv, ænd ˈæstɚɹˌɪsk ˈɛn pˈæsɪv; ðə pɹˈiːfɪksᵻz ɐpˈɪɹ wɪð vˈɛɹiəs ɹᵻlˈeɪɾᵻd mˈiːnɪŋz ɪnðɪ ˌɪndᵻvˈɪdʒuːəl dˈɔːɾɚ lˈæŋɡwɪdʒᵻz ænd bɹˈæntʃᵻz.