Where does “zajtško” come from?

zajtško (Lower Sorbian) comes from Lower Sorbian -ko, from Proto-Slavic -ъko.

Ancestry of “zajtško”, step by step

StepLanguageWordMeaning
1Lower Sorbian-koadded to neuter nouns to form a diminutive
2Proto-Slavic-ъko—
Every word from Proto-Slavic -ъko →Every word from Lower Sorbian -ko →