One constant over that time is an enduring, sinister slur: that the Yazidis are devil-worshippers.
People of that faith say the Islamist rebels rampaging through Iraq have a deeper reservoir of hatred for them than for other minorities in the region, spurred by a misunderstanding of their beliefs.
"It's true that they target other minorities. But they target Yazidis very, very specific(ally)," said Khidher Domle, a Yazidi volunteer who is working to help the small minority who've managed to escape the siege on Sinjar mountain.
"We want people to know us. We are a very peaceful religion. We are also a very old religion."
He spoke in a phone interview from Iraq, as U.S. military planes began food deliveries and airstrikes against the al-Qaida splinter group, the Islamic State of Iraq and the Levant.
Thousands of his beleaguered brethren are now stranded on the mountain, struggling to survive the heat and hunger but fearful of descending toward the murderous mob waiting below.
Domle speaks English, although he's most fluent in Kurdish. Like many Yazidis, he considers himself ethnically Kurdish — although, like seemingly everything else about the culture, the question of its origins is a matter of some debate.
"Accounts of Yazidi origins were particularly malleable to varying political agendas," says a paper by Christine Allison of the University of Exeter in the UK, who has studied the group.
In among the more recent of the numerous displacements and attacks against them, Saddam Hussein uprooted communities and propagated the idea that they were Arabs, to help weaken Kurdish nationalist sentiment in northern Iraq.
Their history is largely oral.
This has left huge discrepancies in descriptions of the religion, whose estimated 700,000 practitioners are spread over different countries, mainly in Iraq but also in Syria, Armenia, Russia and the West.
There are prohibitions against eating pumpkin, fish and lettuce, which is considered unclean. The colour blue is sacred, not suitable to be worn in human clothing.
But the 4,000-year-old religion includes some tenets that might be recognizable to people of other faiths from Zoroastrianism to the three modern-day Abrahamic religions.
This includes one particular deity who inspires the fascination of outsiders and, tragically, also loathing.
He is the fallen angel.
This angel defied the creator, and he's thought to occasionally appear as a serpent. He's also said to have tempted the first humans.
Malak Taus is considered by Yazidis to be the first, and by far the most important, of the seven angels created by the almighty. While he's believed to appear in different forms, he's best known as the Peacock Angel.
While that might sound a lot like the Judeo-Christian-Muslim story of Satan, there are huge differences: Malak Taus is believed to have reconciled with the creator; he's believed to have helped save humanity; he doesn't bear any resemblance to the horned, pitchfork-wielding malevolent figure in other traditions and, perhaps most importantly, the Yazidi religion doesn't describe the world in the same good-or-evil, either-or-type duality as some major faiths.
"People think we worship the devil. But it's not true. We just respect the devil — who is one of the angels in our mythology," Domle said.
"We say he saved humanity when he told Adam, 'You should come out of the garden.'... We have a different name for the devil, we have a different role for the devil."
The group has been targeted by ISIL since the early days of the terrorist organization, when it was known as al-Qaida in Iraq and was led by the now-deceased Abu Musab al-Zarqawi.
Marrying outside the group is a major taboo for Yazidis.
In 2007, a 17-year-old Yazidi girl, Du'a Khalil Aswad, was stoned to death in Iraq, reportedly for being in love with a Muslim boy. The gruesome scenes were captured on video and posted on the Internet.
Hundreds of Yazidis were then killed in a series of terrorist attacks in the following months, with news reports suggesting a retaliatory link to Aswad's stoning.
Allison said Yazidis are grappling with how to adapt their faith to modern times.
Marrying outsiders is the subject of one debate. So is the idea of a more formal codification of the faith so that, according to one example cited by Allison, all followers might have a similar answer to fundamental questions like, "Do Yazidis believe the Sacred Hymns came down from heaven?"
But there are risks, she wrote.
"If Yazidism does not continue to adapt to its environment, especially in the diaspora, in thirty years' time the community is likely to have decreased enormously in number. Many community elders are worried that it may die out altogether, and some are beginning to ponder large-scale reform of such previously sacrosanct areas as the endogamy laws," she wrote in a paper for the Journal of Kurdish Studies.
"However, such radical strategies may well provoke a schism which would weaken the community further."
For now, there are different opinions — even on that mountaintop — about how to perceive the new American involvement in their cause.
"People have been waiting for this... They trust the Americans to get them out," said lawyer Hussam Abdullah, speaking through an interpreter in a phone interview from Dohuk, Iraq. He said he's been in touch with people on the mountain.
"They were very happy. People are dying, and no one can help them."
Domle offers a more guarded view.
He said he was working Friday to find lodging for about 125 families that had managed to flee the mountain, despite the gunfire of ISIL fighters. And he said they were less than impressed that it took so many days, to receive so little help from the international community.
Even the food drop was insufficient, he said.
Domle said he'd heard that many of the supplies were dropped onto the safer side of the mountain, while most of the people were stuck on the other side, facing the rebels.
"Today it is better than two days ago, but they say it is still not enough," he said, after meeting some who fled. "Yazidi people believe Western countries can do things — but they don't... They don't believe Americans really care about the Yazidi....
"I heard this sentence from more than 20 people: 'We don't believe we have any friends.'"