"plum brandy of Central and Eastern Europe," 1885, probably via German, ultimately from the Slavic words, from Old Church Slavonic sliva "plum," which is possibly from the same source as sloe (q.v.).
Entries linking to slivovitz
sloe n.
"fruit of the blackthorn," a small, bluish-black drupe, Middle English slo, from Old English slah (plural slan), from Proto-Germanic *slaikhwon (source also of Middle Dutch sleeu, Dutch slee, Old High German sleha, German Schlehe), from PIE *sleiə- "blue, bluish, blue-black" (see livid). The Balto-Slavic words (Russian sliva, etc.) are perhaps from the same source.
The vowel has been influenced by that in the old plural form, which according to OED persisted into the 17c. Scottish slae preserves the older vowel. Sloe-eyed is attested from 1804; sloe gin is recorded by 1878.