Lunkhead

Lunkhead was an insulting nickname that was meant in jest rather than cruelty.

In 2367, Data called Geordi La Forge a lunkhead after the chief engineer questioned if Data was visiting USS Enterprise-D's salon for a haircut. He explained to a confused La Forge that he was experimenting with friendly jibes and insults and didn't mean to hurt him. Geordi suggested Data not try insulting Captain Picard thusly.

Data related this incident in a letter addressed to Commander Bruce Maddox, which was intended to describe a typical day in the life of the Soong-type android. The letter detailed these events with a focus on Data's observations regarding friendship. (TNG: "Data's Day")