ITIL history

ITIL®, or Information Technology Infrastructure Library, was created in
the late 1980’s in UK Government. The CCTA (Central Computer and
Telecommunication Agency) started writing the books which would become
the IT infrastructure Library in an aim to use best practice IT
Management to increase the visibility and accountibility of IT Services
and to ensure a better cost justification.

The library consisted of approx. 42 books, divided in several sets (see illustration below).

This is the reason why we still talk about the "Service Support Set" when we refer to the blue Service Support Book.
Each set contained several books that focused on a specific topic.