How do I choose a Google developer name?

According to the official Google employee report, 27,169 software engineers work at Google (i.e. research & development) (source).

Developer name

Google Jeff Dean is one of Google’s most popular engineers, ever. The software genius is widely credited by Googlers for the blazing speed of the company’s famed search engine. Dean has been with Google since 1999 and his engineering prowess and popularity have inspired “Jeff Dean Facts”.