High Quality Content by WIKIPEDIA articles! BlackBerry thumb is a neologism that refers to a form of repetitive strain injury caused by the frequent use of the thumbs to press buttons on PDAs, smartphones, or other mobile devices. The name of the condition comes from the BlackBerry, a brand of smartphones that debuted in 1999. Part of the rationale is that the thumb does not have the dexterity that the other four fingers have, and that it is especially common in those who use these devices for such activities at high speeds comparable to that of touch typing.