In the Old Polish and Middle Polish periods there existed deverbal nouns with the formant -ek, such nalazek, przepadek, spisek and others. Witold Doroszewski called them nomina acti. They are also found in Księgi gromadzkie wsi Kasina Wielka. Nowadays, the prefix-ek doesn’t serve this function.
Between 16th and 18th century there existed (and it still can be observed today) a group of masculine personal names ending with a in nominative singular. The declension system of the group was not stable; it was chaotic and allowed for the existence of various variant endings: parallel and alternative endings, or masculine and feminine ones. The system became stable in the 18th and 19th century.
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