micky wrote

Ancestry.com became a publicly traded company on
NASDAQ (symbol: ACOM) on November 5, 2009, with
an initial public offering of 7.4 million shares priced at
$13.50 per share, underwritten by Morgan Stanley,
Bank of America, Merrill Lynch, Jefferies & Company,
Piper Jaffray, and BMO Capital Markets.[26]

https://en.wikipedia.org/wiki/Ancestry.com

What does underwritten mean here? I see it all the time wrt IPOs.

It means that the if the general public chooses not to
buy all the shares at the issue price, the underwriter is
obliged to buy all the shares that the public doesn't want.
https://en.wikipedia.org/wiki/Underw...s_underwriting

Underwriters are used for insurance because someone has to
agree to pay if there is a large claim or a slew of smaller claims.

But IPO's take in money. What are those 4
companies underwriting, what are they doing?

See above.

Why can't some bookkeeping company with no assets just
sell the stock and take in the money for ancestry.com?

That doesn't raise as much money if the stock isnt popular.