This article deals with the origin of the three distributive pronouns of the Baltic languages: Old Prussian erains, Lithuanian kiekvíenas, Latvian ikviêns ‘everybody, everyone, each one’. They are all characterised by the numeral ‘one’ (OPr. ains, Lith. víenas, Latvian viêns), originally used as a pronominaliser, but they differ in their first element, which derives from a preposition ‘until’ in Old Prussian (er), from a conjunctive adverb ‘how much’ in Lithuanian (kíek) or from a form that could have been both of them in Latvian (ik ‘as much as’, but Lith. ikì ‘until’). The aim of this paper is to explain the formation of these distributive pronouns and to account for their differences. It can be argued that the most ancient formation derives from a conjunction ik ‘as much as’ > ‘as long as’ > ‘until’ reanalysed as a distributive marker (Latvian), whereas Lithuanian kiek- and Old Prussian er- are recent modernisations of ik-.