The article attempts to differentiate, on the basis of selected words recorded in the Polish-East Slavic borderland, whether we are dealing with language loans or old references. The analysis takes into account e.g. ethymological, morphological and geographical criteria. The study focuses on the following words: cot ‘an even number’, czapigi, czepigi ‘plough handle’, had ‘an abominable animal’ and hydzić się ‘loathe’, ‘abhor’, ‘denigrate’, kosiec ‘scyther’, liszka ‘an odd number’, liszny/liszni ‘superfluous’, ‘supernumerary’, przewiąsło ‘a straw belt to tie sheaths siewiec ‘sower’, śloza ‘tear’, żeniec ‘harvester’, żenich, żeniuch ‘bridegroom’, ‘fiancé’, żnieja ‘female harvester’. Recognition as borrowings may be based on those word forms where phonetic elements characteristic of other languages, unknown in Polish, occur. Analysis of certain words has revealed the occurrence of Proto-Slavic and all- -Slavic words, preserved in the Polish language as relics, in peripheral areas. In some cases, it is difficult to make clear-cut decisions, because, for example, the stem of the word is a continuation of the Proto-Slavic forms, to be found in the Polish language, while the derivatives are borrowings.