Tailgate parties are a hallmark of so-called "bro country," a backward-baseball-cap-wearing trend in country defined by trucks, parties, women in tight jeans and a seemingly unlimited supply of beer. These tailgate parties are less about barbecues with friends at sporting events and more about raging down a dirt road or cutting loose in a farm field on a warm summer night.

In recent years, tailgates are seemingly everywhere in country, having been referenced in such hits as Luke Bryan's "That's My Kinda Night," Randy Houser's "Runnin' Outta Moonlight," Brantley Gilbert's "Kick It in the Sticks" and Jason Aldean's "My Kinda Party," an anthem whose lyrics and powerhouse chords helped define the trend. "You can find me in the back of a jacked-up tailgate," Aldean sings, "chillin' with some Skynyrd and some old Hank."

Not everyone is happy about the trend, though. "If I hear one more tailgate in the moonlight, daisy duke song, I'm gonna throw up," Zac Brown famously said during a radio interview last year. He went on to call Bryan's song "That's My Kind of Night" (which was at that point rising fast on the charts) "one of the worst songs I've ever heard." Ouch.

Unlike other common tropes populating today's country music, though (trucks and beer, for instance, or even tributes to Hank Williams), tailgate parties are a recent phenomenon.

Ten years ago, such references were few and far between, and a generation ago, if a singer mentioned "tailgating," it was of the "following too close" variety. "I got a memory on my tailgate, and old Smokey's on my rear," sang Johnny Paycheck in "his 1980 hit "Drinkin' and Drivin'."

So who started the whole tailgate trend? Let's turn the dial back to the 1990s and start with the catalog of one of the era's biggest hitmakers: Joe Diffie.

Diffie's 1990 song "Almost Home" is one of the first country hits that mentions a "tailgate." Though to be honest, it's not quite in a "party all night" context. Instead of beer or BBQ, his truck bed is full of fishing equipment. "Cane poles on the tailgate bobbers blowin' in the wind," Diffie sang.

Three years later, though, Diffie brought up tailgating again in his hit "Pickup Man." And this time, the reference feels more in line with the trend in today's country:

You can set my truck on fire, and roll it down a hill
But I still wouldn't trade it for a Coupe DeVille
I've got an eight foot bed that never has to be made
You know if it weren't for trucks we wouldn't have tailgates
I met all my wives in traffic jams,
There's just something women like about a Pickup Man