CHIMO is derived from the Inuktitut language. According to folklore, when two people met on the Arctic tundra, they rubbed their chests in a circular motion and said, "Chimo" , meaning "Are you friendly?" The answer was a repeat of the gesture and the word "Chimo!" ("Yes, I am friendly!)
The salutation has been adopted by the military engineers, (without the "chest thumping and rubbing", at least, most of the time:-), and when two engineers (or more) meet, the word will be definitely heard.
If you, on parting company with an engineer after first meeting Her/Him, - have been accorded the parting word "CHIMO", then be assured you have made a new friend, and have been deemed worthy to be a friend to the engineer "Family."