From Wiktionary, the free dictionary
Sclav (plural Sclavs)
- Archaic form of Slav.
1886, The East, page 751:If Russia succeeds in gaining the leadership of the Sclav races [...]
1905, The International Quarterly, volume 10, page 36:The fall of Poland left Russia the sole representative of the Sclav among the kingdoms of the earth.