The author of the article considers examples from the Baltic and Slavic languages in the works of the Russian and Czech linguist Čeněk Šercl from the point of view of etymology. The author comes to the conclusion that an attempt to etymologize some words of the Latvian language was made by Šercl before the appearance of Mühlenbach-Endzelīns dictionary and in many cases is confirmed by the data of modern etymological science. Latvian puppikis 'hoopoe' – onomatopoeia, after the cry of this bird (“In German, the cry of this bird is depicted through huppuppupp, compare with this the following names of hoopoe: Latin upupa, Latvian puppukis, French puput <...> Persian bûbû”). In the Mühlenbach-Endzelīns dictionary we find: “puputis der Wiedehopf. Onomatopoetisch <...>”. Šercl also actively uses examples from the Slavic languages and in many respects anticipates their etymological interpretation (see, for example, Šercl's arguments about the Slavic lexeme *perper- and the data of the EDSL).