more on "gen up" and "gin up"

[Jonathon Green]

'Gen' as meaning information is not computerspeak but an RAF coinage -
Partridge suggests as early as 1929 - which was widely popularized during
WW2. It is, supposedly, an abbreviation of 'general information of all
ranks.' He also has 'genned up': = well supplied with infomation, listed in
the Dict. Forces Slang 1939-45 (1948), although 'gen up, is defined only as
'to swot for a test or examination; to read up a subject'. In addition he
lists 'gen king' or 'gen wallah': 'one who can be tapped for trustworthy
information', and 'gen man': (1) an Orderly Room, Signals or Operations Room
clerk; (2) an Intelligence Officer. A 'gen box' was a synonym for a 'black
box', either an instrument that permits bomb aimers to see through clouds or
darkness.

After the war it moved into civilian use, thus

1945 Kingsley Amis letter 15 Dec (in Leader _Letters of KA_, 2000) 23: I
will then slip the gen across to you ole boy

Jonathon Green