What I did was simply go through every pair of letters in the entire alphabet systematically and tried to match each to a real-world entity. Starting with AA, AB, AC and going all the way to ZX, ZY, ZZ you will consider 676 pairs (26 times 26). It is interesting to see how many answers you can come up with, and also how many you can't. I'm sure every person's list will be different. Here's how mine started off:
AA - American Airlines, Alcoholics Anonymous
AB - Alberta (province of Canada)
AC - air conditioning
AD - Anno Domini (Year of our Lord)
AE - initials of the poet A.E. Housman who wrote "When I Was One And Twenty" and "Loveliest Of Trees, The Cherry Now"
AF - Air Force
AG - Attorney General
AH - Anno Hegirae (Year of the Hijrah), the Islamic calendar which commemmorates the beginning of the Prophet Mohammed's journey from Mecca to Medina in 622 AD
AI - artificial intelligence
and so on through AZ (Arizona) and on to BA (Bachelor of Arts), all the way to ZZ. It may take awhile. Several days. Several months. Knowing the periodic table helps (AU is gold, FE is iron, PB is lead).
The only rule is that each answer must come out of your own memory banks spontaneously without referring to anything in a book or on your phone or computer.
It won't put you to sleep, though. Just the opposite, actually. It will keep you awake. To go to sleep, try doing something really useful like praying for your family and friends. It works every time because our old enemy doesn't want us to do that, ever.
This has been another
P.S. - PB is also peanut butter.