Brodie RobertsonCanonical called it Unity because it was supposed to "unite" all your device interfaces, PC, phone and yes even TV.
10-volt@BrodieOnLinux honestly what Ubuntu was trying to do was extremely promising, and the fact that it was a solid distro at the time, its a shame what its like now
Mr. Matt 
@10volt @BrodieOnLinux Agreed. It was Unity's design that really sold me on GUI-based Linux. To this day my GNOME installs still have Dash-to-Dock with everything on the left, mimicing Unity.