Dottie and Dot are old Dorothy nicknames that some cutting-edge Brits are bringing back to fashion. It's been half a century since Dottie ranked on its own in this country, one of those nickname names that flourished in the 1890's.
Probably the most prominent bearer of the name was the seminal country music singer Dottie West--born Dorothy, of course. In the movie A League of Their Own, Geena Davis's leading character Dottie Hinson was based on real life women's pro baseball player Dottie Kamenshek.
Dot can make an adorable middle name--if your last name isn't Com.