David Karp’s software consulting company, where Tumblr development began, was called Davidville.
Karp founded Davidville after working at UrbanBaby and selling his shares in that company. It combined paid software-consulting projects with Karp’s own product experiments. Marco Arment joined Davidville as an engineer, and the two began developing Tumblr during a two-week gap between client contracts in 2006.
Karp had been interested in tumblelogs, a form of short-form blogging, and had waited for an established blogging platform to offer a dedicated service. When that did not happen, Davidville became the setting for building the alternative. Tumblr launched in February 2007 and quickly attracted users.
Davidville was eventually shut down as a consulting operation because Tumblr consumed Karp’s attention. In October 2007, it was renamed Tumblr, Inc. The other options refer to different companies associated with blogging or internet history, not Karp’s consultancy.