Why does Nivkh have reindeer terms borrowed from a Manchu-Tungus language?

The Nivkh language contains reindeer terminology borrowed from a Manchu-Tungus language, though these terms do not appear to originate from any of the Tungusic groups with which the Nivkh are currently in contact.1

This linguistic phenomenon is considered a complex loan relationship. While the Nivkh people are traditionally coastal sedentary hunters and fishers who historically relied on dogs as their only domestic animals, their contact with the Evenk eventually introduced the reindeer as a draft animal. The presence of these specific, non-local loanwords suggests ancient interactions with a Manchu-Tungus-speaking population that are no longer directly reflected in the Nivkh's modern geographical or social environment.123