Shanghai 伤害 is a Chinese verb meaning "hurt". Would that mean that "shanghaiing" someone is "actually" a euphemistic reference to the injury suffered by enslaved sailors?
It's an English word; it's got nothing to do with Chinese.
I was asking after the etymology, actually; were whoever coined the term aware of the meaning in Chinese? (Compare eg pagerank or bakers' chocolate elsewhere in thread - named after a proper noun, but the term as used is a description - but in this case it would be the reverse - named after a description, but the term as used references a proper noun.) Rereading I agree that wasn't obvious, though.
It's an English word; it's got nothing to do with Chinese.