ENThe conflict of national Polish and Lithuanian historiographies typically involves divergent interpretations of the shared history, but it is seldom noticed that linguistic interpretations (including the onomastic ones) may be divergent too. These linguistic interpretations can also become a tool of language policy, especially of the policy focused on personal names. The present article analyses selected examples of genetically Lithuanian surnames currently in use in Poland which in some Polish linguistic sources are etymologised as genetically Polish, as well as – conversely – those of Polish origin which in some Lithuanian research are interpreted as genetically Lithuanian. Although inadvertent and accidental mistakes cannot be ruled out, in the case of homonymic surnames there is a visible tendency to give priority to native etymologies. It may be assumed that for the society at large, the origin of a surname somehow implies the nationality of its bearer; in the case when the researchers’ attitudes are nationalistic, this fact may be used as an argument in public debates whose scope far exceeds that of onomastics. [From the publication]