Slavonic adj.

"one of the people who inhabit most of Eastern Europe," late 14c., Sclave, from Medieval Latin Sclavus (c. 800), from Byzantine Greek Sklabos (c. 580), from a shortening of Proto-Slavic *sloveninu "a Slav," which is probably related to *slovo "word, speech," which suggests the name originally identified a member of a speech community (compare Old Church Slavonic Nemici "Germans," related to nemu "dumb;" Greek heterophonos "foreign," literally "of different voice;" and Old English þeode, which meant both "race" and "language").

Max Vasmer, the authority for Slavic etymologies, rejects a connection to *slava "glory, fame," which, however, influenced Slav via folk etymology. This word is the -slav in personal names (such as Russian Miroslav, literally "peaceful fame;" Mstislav "vengeful fame;" Jaroslav "famed for fury;" Czech Bohuslav "God's glory;" Latinized Wenceslas "having greater glory"), and is perhaps from PIE root *kleu- "to hear."

The reduction of scl- to sl- is regular in English (compare slate). In late 18c. and early 19c. The spelling Slav is by 1866; in English it also was spelled Slave, influenced by French and German Slave. As an adjective, belonging to or characteristics of Slavs, from 1876.

"of or pertaining to the Slavs, their language, literature, etc.," 1813, Sclavic, in reference to the language; see Slav + -ic. Earlier in the same sense was Slavonic (1640s). Slavian is attested by 1836. As a noun, in reference to the Slavic languages collectively, one of the primary groups of the Indo-European family, by 1812.