propeller head (or propellor head, prop head, prophead)

A propeller head (also spelled propellor head , and sometimes shortened to prop head or prophead ) is jargon for someone who is exceptionally, perhaps weirdly bright or knowledgeable, especially in some technical field. In computers, according to The New Hacker's Dictionary , it's a synonym for computer geek . The term refers to the child's beanie cap that comes with a spinning propeller sticking out of the top.

The New Hacker's Dictionary says that the propeller cap somehow became a self-parody symbol of the out-of-this-worldness of science fiction fans. It attributes the idea to science fiction writer Ray Faraday Nelson. We like this tongue-in-cheek definition from The Web Developer's Journal :

" The term 'prophead' is a holdover from the days when the nerd kids on the block wore caps with little propellers on top. This fashion gave way to the pencil pocket protector. Here at the WDJ, 'propheads' refers to programmers, developers and other technically-oriented types. A weenie doesn't even use a regular keyboard, just a little one with two keys: 1 and 0. Weenies talk among themselves in continuous data streams, which sound to mortal ears like a modem logging on."