It is a known fact that there are three blocks of IPv4 Addresses that were chosen to be reserved for private networks:
10.0.0.0 - 10.255.255.255 (10/8 prefix) 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
(as specified by RFC 1918). However, although I can sort of see why 10.0.0.0 would be a natural choice, I can think of no particular reason why 172.16.0.0 and 192.168.0.0 were chosen among all the possibilities. I tried to google about this but got nothing, and the RFC document did not provide any explanation either. Was it really just a random decision?