It's also worth noting that the ADM-3A terminal may have chosen H/J for left/down due to ^H being backspace (like left) and ^J being newline (like down) as well

It's also worth noting that the ADM-3A terminal may have chosen H/J for left/down due to ^H being backspace (like left) and ^J being newline (like down) as well as being on home row.