[TYPES] Historical question: origin of the ":" symbol

[Ezra Cooper]

On May 26, 2008, at 2:51 PM, Edsko de Vries wrote:

> Can anyone refer me to a discussion of the history of the symbols used
> in type theory? In particular, the origin of the ":" symbol? I seem to
> recall reading somewhere that is derived from \epsilon, which in  
> turn is
> the first letter of 'esti' (to be), but I cannot remember where I read
> this -- might have made it up myself :)

This may not help, but Paul Taylor briefly discusses the history of  
the subset symbol in "Practical Foundations of Mathematics," page 75.

Ezra