Garrett said something triggered this donor to make all these donations. Maybe a spouse died. Maybe they are dying or already died and requested their estate to make the gifts.
Whatever the answer, Garrett predicted it would take a long time to crack the code.
Like many others, Melissa Berman, who runs Rockefeller Philanthropy Advisers, a New York-based advisory service for donors, suggested that it was probably a female.
"I think the most obviously clue is that these are all institutions run by women," Berman said. "Most of them of are public institutions and that much of the money is designated for scholarships for low-income or disadvantaged students. So that tells me that this would be an individual who is or was very concerned about issues of access to opportunity."
That doesn't necessarily mean they are a self-made millionaire or somebody who comes from a poor background.
"It's also possible that it was somebody who had means but recognized how fortunate she was and how life-altering higher education is," Berman said.
Reading further into it, Berman suggested that the donor is an older woman who is not used to being in the public eye.
"It's the anonymity that's really so interesting and such an unusual feature," Berman said. "Most people wouldn't think that there's any problem with being identified as being a multi-million donor to a public institution for scholarship funds, especially people who are self-made and who are younger or middle-aged, including the baby-boomer generation."
It's the World War II generation, she said, who tends to shy away from publicity.
"An elderly women who inherited money either from a family or a spouse might not be as comfortable being in the spotlight if she wasn't in the spotlight a lot during her life," Berman said. "I think people who are self-made and successful are comfortable with attention."
So why all this secrecy?
"This person doesn't want to be turned into another Bill Gates and hear from everybody under the sun," the University of Pennsylvania's Gelles said. "The economy has really wreaked havoc with donations. If you're still in a position to make a donation, you're not exactly going to want to advertise it because hungry institutions having a difficult time meeting their budgets, who do worthy things, are going to descend on you if they think you have the capacity and might be even modestly related to their mission."
Anonymous donations are up in this down economy, according to the Chronicle of Philanthropy.
From June 2008 to April 2009, there were 80 anonymous gifts tracked by the publication of $1 million or more. That's nearly 19 percent of the 422 total during that period. In the past decade, the proportion of large gifts that were made anonymously has ranged from 3 to 5 percent.
"This is clearly somebody who wants to move a needle and is at a stage in life where it is important to do," Gelles said. "I'm thinking they are not young because young people generally don't know who they are yet and want more publicity."