One of the mysteries of the English language finally explained.
Also more fully "Gunning fog index". A measure of the readability of a piece of English-language text, expressed as the number of years of formal education thought to be needed to understand the text.
1940s; earliest use found in Journalism Quarterly. From fog + index.
fog index/ˈfɒɡ ˌɪndɛks/
In this article we explore how to impress employers with a spot-on CV.