BlackBerry thumb
n. A repetitive stress injury characterized by swelling and pain at the base of the thumb and caused by prolonged use of the thumb while operating a BlackBerry or other personal digital assistant.
There's a new indicator of the physical downsides to text messaging. A study from the U.K. finds that 38% more people suffer from sore wrists and thumbs due to "texting" than five years ago and 3.8 million people now complain of text-related injuries every year. This, of course, follows the recent revelations of people suffering from "BlackBerry thumb."
—Tom Smith, “When Tech Hurts,” InformationWeek, February 21, 2006
Repetitive motion injuries, which have long afflicted desktop and laptop computer users, are invading the mobile handheld world.

There's even an informal name for the malady — "BlackBerry thumb" — a catch-all phrase that describes a repetitive stress injury of the thumb as a result of overusing small gadget keypads.
—Alicia Chang, “Blackberry Users Learning Painful Lesson,” The Associated Press, October 20, 2005
2002 (earliest)
Thumb typing on gadgets the size of pagers has almost moved mainstream. Only a year ago, most people would've thought thumb typing was as bizarre as trying to play piano with your elbows. Now it's more common. But some everyday professionals are developing thumb tendinitis — a.k.a. "BlackBerry thumb" — forcing them to give up thumb typing and any other thumb-related activities.
—Kevin Maney, “Tech firms fiddle with tiny keypads,” USA Today, January 29, 2002