Where does “Slezsko” come from?

Slezsko (Czech) comes from Czech sléz, from Old Czech sléz, from Proto-Slavic *slězъ — mallow.

Ancestry of “Slezsko”, step by step

StepLanguageWordMeaning
1Czechslézmallow any of a group of plants in several genera of the taxonomic family Malvaceae
2Old Czechsléz—
3Proto-Slavic*slězъmallow
Every word from Proto-Slavic *slězъ →Every word from Old Czech sléz →Every word from Czech sléz →