It's definitely not common in America, where it's more commonly used in, e.g., a parting of ways with a close friend or relation for a journey ("see Johhny off [to the airport for college]").
That's the sense I understood this in. That the fish doesn't defeat the piranhas or "fight them off", but it can ignore them until they give up because of the armor, and then bid them goodbye.
By ”general English” I assume you are meaning American English?
"general English" reasonably applies to the common subset of the language.