The etymology of "Boffin" :
The term Boffin as it is used now seems to have come from the RAF in the 1930's. A distinctly british word, its meaning implies far more than just being "techie". To describe someone as a boffin implies a certain degree of absent mindedness as well as being very bright. There is a definite degree of mad scientist about it as well. Boffin also implies that the work being done is of a military nature.
Possibly the best example of a classic boffin would be the character Q from the James Bond films. For those people who haven't seen any of these films Q is a scientist working for MI6. He is the person who creates the infamous bond gadgets, but he is also slighty mad and highly absent minded.
The first "boffins" were a group of scientists who were asked to work for the RAF in the mid-1930s. A group of electrical engineers and physicists who worked at Bawdsey Research Station in Suffolk developing the world's first radar systems.
The origin of the word Boffin seems to have come from a book by Charles Dickens. In his work "Our Mutual Friend" one of the main characters is called "Mr. Boffin", although I can't find a reason for why this word might have become used to refer to these scientists in the RAF. It's possible that it was used simply because its a cool sounding word *g*.
My thanks to estemeed noder Oolong for adding some extra enlightment for me. He points out that according to Brewer's Dictionary of Phrase and Fable, this term might have come into being from a scientist who liked to give his colleagues Dickensian nicknames.
There is also a family of hobbits in Tolkien's works that are called the Boffins, but I don't think they worked on radar.