Knox sounds like NOx (pronouced nawks) which is a term used in the oil & gas industry for emissions from combustion sources. Also a byproduct from car engines.
In Scotland at least this name will always be associated with John Knox, the Calvinist preacher who was one of the leaders of the Scottish reformation.
Bernard Knox, literary scholar. He wrote prefaces for many of Robert Fagles' translations, such as the Iliad, Odyssey, and Aeneid (they're both absolutely amazing!)
My nephew is named Knox and I happen to like it very much. A name shouldn't be defined by its meaning. It's a name, someone's identity. Knox is a very nice name and I think it's an easy name to carry through life and won't get old. Love it!
I actually find this name strangely alluring, surprisingly enough. I suppose I relate it to Fort Knox, which makes me think of terms along the lines of "Strong; Loyal, Committed; Faithful; Powerful; Determined; Brave; Courage", but I am aware those definitions are a far cry from the actual meaning. The image of a barbed-wire fence cannot seemingly leave my mind, either.
Would I use it as a name, though? Regrettably or not, no.