Unless new evidence is uncovered either showing clear signs of transition or something providing definitive proof that the word originated in ancient Korea, this will be more of a pseudoscientific language comparison.
At the risk of being scolded for logical leap, I have an amateurish idea that Japanese "samurai" has some connection to Korean "ssaurabi".
[2][3] The 2002 South Korean film Saulabi (variant romanization of ssaurabi), directed by Moon Jong-geum, dealt with this theory.
Linguistically, it is hard to explain the similarity between ssaurabi and samurai with regular correspondences between Korean and Japanese.
[citation needed] Another problem is that the word samurai, perhaps contrary to popular belief, originally had nothing to do with fighting or being a warrior.