Today, in my Teaching Math to ELL students class we interviewed students from different countries around the world to find out about the way they learned math. Interestingly, most learned their multiplication facts to 9 x 9 while some learned to 10 x 10 and one student from Saudi Arabia learned up to 19 x 19. No-one seemed to learn to 12 x 12.
10 x 10 is the usual limit for remembering the facts but I always have wondered why it was, traditionally, 12 x 12. Perhaps it was because 12 figures so large in our Western culture (12 Apostles, 12 months in a year, 12 hours in a day, 12 in a dozen, twelfth day of Christmas, 12 inches in a foot etc). Perhaps there is a more logical reason? I can't find an answer on Google, yet.