First attested in 1688 in the nautical sense. Borrowed from Dutch boord or German Bord.
борт • (bort) m inan (genitive бо́рта, nominative plural борта́, genitive plural борто́в)
- (nautical, aviation) board, side
- (aviation) aircraft, flight
- breast (of a jacket or coat)
- Vasmer (Fasmer), Max (Maks) (1964–1973), “борт”, in Etimologičeskij slovarʹ russkovo jazyka [Etymological Dictionary of the Russian Language] (in Russian), translated from German and supplemented by Trubačóv Oleg, Moscow: Progress