[Nick Beale]

I'd always understood it to be a night fighter control sector of some kind but I didn't know about the forestry definition (thanks for adding to my vocabulary!). I'd guess that the term was taken up by analogy.

Addition: Checking my German Miliary Dictionary (facsimile of a 1944 US War Department publication), it gives the almost the same definition Larry does: "sub-area of forest (for mapping purposes)".

Cassell's New German Dictionary (1965) has for the noun: "hurry, rush, hot pursuit, galloping; hunting, chasing, shooting; shooting preserve, game reserve."

I suppose that a defined area where you can shoot things is a reasonable analogy for a night fighter zone.