eBay - Pierre Omidyar, who had created the Auction Web trading website, had formed a web consulting concern called Echo Bay Technology Group. “Echo Bay” didn’t refer to the town in Nevada, “It just sounded cool,” Omidyar reportedly said. Echo Bay Mines Limited, a gold mining company, had already taken EchoBay.com, so Omidyar registered what (at the time) he thought was the second best name: eBay.com.
Google - a deliberate misspelling of the word googol, reflecting the company’s mission to organize the immense amount of information available online.
Hotmail - Founder Jack Smith got the idea of accessing e-mail via the web from a computer anywhere in the world. When Sabeer Bhatia came up with the business plan for the mail service he tried all kinds of names ending in ‘mail’ and finally settled for Hotmail as it included the letters “HTML” — the markup language used to write web pages. It was initially referred to as HoTMaiL with selective upper casing.
Yahoo - a backronym for ‘Y’et Another Hierarchical Officious Oracle. The word Yahoo was invented by Jonathan Swift and used in his book Gulliver’s Travels. It represents a person who is repulsive in appearance and barely human. Yahoo! founders David Filo and Jerry Yang jokingly considered themselves yahoos
And my personal favorite and most fitting: Lycos - from Lycosidae, the family of wolf spiders.