Canon Rangefinders - Peter Dechert and Peter KitchingmanPeter Dechert is best known for his Canon Rangefinder, Canon SLR, and Olympus Pen books, the latter two long out-of-print. He was a monthly columnist for many years for SHUTTERBUG magazine, and has contributed to many others. Most recently he has written about the pre-WW2 Zeiss 35mm cameras, but his interests in camera equipment and optics are many and varied. As a pro protographer and honorary life member of ASMP, Peter is also expert in using the gear!
Peter Kitchingman - author of Canon Rangefinder Lens book Peter Kitchingman's 'Canon M39 Rangefinder Lenses 1939-71' book is the definitive source on these very interesting optics. His interests also go to the entire Canon Rangefinder system and beyond.
I think I have seen the symbol though not often. Here is a thought. Canon's name originally derived from Guanyin or Kuanyin in Chinese and became Kwanon (in Japanese) and then Canon when transliterated into English. (You can see how these broadly sound something the same when allowing for language differences). Guanyin is the Buddhist Goddess of Mercy. Early cameras were named accordingly and the change to Canon came about due to the desire to market the cameras in the west and Canon is a more western sounding name which never the less still had the same meaning.
In keeping with its Buddhist roots, I wonder if the early logo you mention derived from Buddhism (as its very earliest logo also did - that one represented "Kwanon with 1,000 Arms" and flames.). The eagle symbol is used in Buddhism I understand- though it does not seem to be a central part of it. For example Garuda is the Eagle King in both Buddhism and Hindu culture. In general I would just suggest that maybe the eagle was regarded as a cool symbol taken broadly from eastern culture that westerners would also be familiar with.
Admittedly the above is nothing more than my conjecture based on the company's known history but it may stimulate some other info.