Today is the 15th anniversary of the Thinkpad, and the first model was the the IBM 2521, a pen operated tablet that shipped on July 19th 1992. Reg Hardware, who researched this history, says it had a 20MHz 386SX proc, 4-8MB of memory, a 10-inch 640 x 480 monochrome screen, and a 2.4Kbps modem. OMG, this article is making me feel so old. [Reg Hardware via JKOnTheRun]
I'm fairly certain it's the 15th anniversary of the electronic Thinkpad, but I believe the ThinkPad name goes way older than that.
IBM lore has it that the notepads people used at IBM during meetings was basically custom-printed with the word "Think" on it, thus earning the name "Thinkpad".