The word gross has been in English for hundreds of years. We got it from French, where it means "big" or "fat." It took on a variety of senses in English related to size, including "coarse" (gross grains as opposed to fine), "strikingly obvious" (grosse as a mountaine), and "whole" (gross as opposed to net value). It also picked up negative senses like "vulgar," "crude" (Grose folke of rude affection Dronkerdes. Lubbers, knaues), or "ignorant" (a grosse unlettered people). Uncivilized and indecent behavior was called gross. Low-quality food was called gross. And history is filled with gross abuses, gross misconceptions, gross perfidy, and gross folly. From there it’s not a big jump to the current sense of disgusting. There’s always been something repulsive, or at least unsavory, in the word gross.

Still, “Ew! That is so gross!” has a very modern ring to it. It feels like a very different word from the one they were using 200 years ago. In contrast, a word like disgusting feels essentially the same. So what happened to gross? What separates the gross of today from the gross of the past?

Gross did not undergo a big change in meaning, but it did undergo a big change in context. In the late 20th century, young people started to use it a lot—like, a lot a lot. So much so that old people noticed it, and didn’t like it. As one critic said in a 1971 issue of The Saturday Review, “Gross has always meant something coarse and vulgar. But as used by the teens, it runs the gamut of awfulness from homework to something the cat contributed to ecology.” Gross became slang.

At first, some time in the 1950s, it became an in-group term, one of a number of words (including great, the greatest, the most) that, according to a 1959 article about university slang, were “either complimentary or derogatory depending on how they are said.”

It’s hard to image anyone today using gross in the complimentary way. It’s also strange to learn that, according a 1973 article, grossed out could mean "bored" or "tired" (Bored? Grossed-out? Come to the bistro), or "wild and crazy" (That was a real gross-out party). The early slang meaning of gross was broader than it is now.

The development of the verb form to gross out in the '60s and '70s (probably on analogy with cop out and freak out) helped contribute a sense of newness to the word and made it seem even more slangy. By the '80s it was a staple of “valley girl” speak, so often repeated, mocked, emulated, and imitated that it spread far beyond the teen world it came from. Its sense narrowed into a succinct judgment of visceral disgust, capturing the colorful bodily emotion of “gag me with a spoon” but in a less wordy way. Gross was always there, but young people, needing a more compact package to deliver their disdain, fixed it up and made it grosser.