According to the Chinese zodiac Google became a public company in the year of the Monkey, in August 2004.
In Western culture we are familiar with the story of the three monkeys who very wisely: see no evil, hear no evil, and speak no evil. In some Asian cultures there is a fourth monkey: Do no evil.
"Do no evil" is often misquoted as Google's famous motto, which is actually: "Don't be evil" but it's essentially the same.
In 2015, Google had tired of its responsibilities as the fourth monkey reorganized its business operations; renamed itself Alphabet, and abandoned the problematic old motto and replaced it with the more modern: "Do the right thing."
It's close enough to the old one that it's unlikely to confuse the ethics of the staff; plus, the new motto is sufficiently vague with a phrasing that provides endless relativistic wiggle room to answer any challenge.
An evil temptation...
I was never comfortable with Google's "Don't be Evil" motto because of the company's strategic importance to the Internet and to the economies of entire countries.
As Google grew in size I grew more worried about its "Don't be Evil" philosophy.
We have seen many times how the universe loves irony; and how it values thorny opportunities to pop our oversized hubris and sink our blowhard ambitions -- the bigger the better.
With a motto like "Don't be evil" there was a nightmare risk that Google would somehow end up being responsible for many imaginable and unimaginable evils. The hands of fate love such opportunities. Let us not lead them into temptation!
A less evil motto...
I once proposed a replacement motto for Google, with the aim of lowering the risks of attracting disastrous ironic consequences:
"Brush your teeth and get eight hours sleep."
If Google messes up what's the worst that can happen? It's a bit grumpy, falls asleep in meetings, and has to chew some minty gum. No harm done and it's temporary -- there's always a new day.
But with "Don't be evil" there's no end to the potential horrors from a universe highly motivated by ironic intervention. Google did the right thing to be rid of it.