That's kinda what I was thinking, the Korean use of Neh can be flexible enough to be used as a past particle. The Japanese like to ignore or outright white wash the influence and impact of Korean culture on the island.
i dont know if it really came from portuguese, but 'né?' as a contraction for 'não é?' is a real thing, and it really does match the use of japanese 'ne' and english 'innit'