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o (1) (Conjunction) "or"
10th cent. From Latin aut 'id.' From either *aut-i 'id.' in Proto-Italic. From Proto-Indo-European *h2eu̯ "away."
Indo-European
Romance
Asturian o, Portuguese ou, Galician ou, Catalan o, French ou, Italian o, Romanian au
Italic
Oscan aut "or," Umbrian ute 'id.'
Celtic
Old Irish úa "away," Old Welsh o 'id.,' Middle Breton o 'id.'
Balto-Slavic
Old Church Slavonic u- "from," Russian u- 'id.,' Polish u- 'id.,' Slovene u- 'id.,' Old Prussian au- 'id.,' Lithuanian au- 'id.,' Latvian au- 'id.'
Hellenic
Ancient Greek αὖ (aû) "again"
Indo-Iranian
Sanskrit áva "off," Old Avestan auuā 'id.'