Resumen de Lith. namõ, OCS doma and the PIE directive
The termination of the isolated adverbs Lith. namõ “homewards” and Sl. *dȍma “at home” is traced back to a common Balto-Slavic prototype *-ā, which in turn is argued to go back to a post-Anatolian variant *-oh2a of the PIE directive. The ending *-oh2a was formed through recharacterization of the inherited thematic directive *-oh2 (apocopated from pre-PIE *-o-h2e) with the athematic ending *-h2a. It yielded *-ā in Balto-Slavic, but, probably, *-ō in the Southern languages (Lat. quō “whither”, Gk. ἄνω “upwards”). This proposal finds support in the fossilized compound Lith. žmõgus/žmogùs 'man' (< *dhghm-oh2a-gwh2-u- 'walking on the earth'), and in the o-stem ablative singular *-oHad > OLat. -ōd, Gk. dial. ϝοικ-ω, but Bl.-Sl. *-ā(d) (Lith. -o, OCS -a).
