Common dictionary words are not trademarkable. In fact, if an existing trademark becomes common in speech it becomes genericized and the trademark is lost. One of my personal hobbies is doing that to Velcro.

That, and you've got to remember how big iPods were at the time. In 2007, it was weird that Apple was entering the cell phone market. The iSomething branding basically saved the company in 2001 with the iMac and iBook, the iPod was the first electronics gadget I ever remember being worn as a status symbol, the first that got treated like designer clothing or shoes. That "I have an iPod, and you have...whatever that is." White headphone cords were a fashion statement. The Motorola Razr phone got the same treatment before the iPhone.