The origins of Grunts were back on The Twisting Nether server, where founders Dreadbeard, Wyldfire, and Bloodreaver moved from a dwarf-only guild called Ironforge Regiment to form another guild, Sgian Dubh. Many classic elements of Grunts Role-playing, including salutes and Taking the Black, originated with those guilds.
However, Twisting Nether turned out to be too established of a server to let the guild take off, so it moved to The Venture co. on its release date, and Dreadbeard/Dreadangus and Wyldfire founded GRUNTS, taking the name from the sci-fi/fantasy novel by Mary Gentle.
Grunts quickly became one of the largest guilds on The Venture Co., and they were fixtures in all sorts of World PvP events. Many world PvP skirmishes started because the alliance provoked a Grunt and got more than he expected in return.
In addition, Grunts maintained a rivalry with Alliance guild Order of the Ancients, responding to their leader, Recruiter's, egotistical personality and overblown forum rhetoric by doing their part to prevent the server opening of the Gates of Ahn'Qiraj, including the WE BANDAGE - SO YOU DON'T GET INTO AHN'QIRAJ Christmastime event and countless world PvP battles.
In the months before the release of The Burning Crusade, many Grunts members were taking advantages of the changes to the honor system to run battlegrounds for newly-obtainable gear, while others left the guild to focus on PvE. After the release of Burning Crusade, the guild leadership became more and more PvE-focused, while other members felt left out of the PvE progression, leading to another major split, which saw the guild leaders as well as several officers leaving the guild. Leadership passed to a few of the longest-standing members who remained, including Darkened, Zylaxice, and Odawa.
Since then, Grunts continues to go strong in roleplaying, world PvP, organized battlegrounds and arena teams. One of the newest developments is its new set of standards for Grunts Raiders, aimed at creating a group of Grunts dedicated to PvE progression through Karazhan and beyond.
Many thanks to Bloodreaver for information on the early history of Grunts.