> (Their earlier computers may have been big-endian too, I'm not sure.)
Yes, their choice of big endian probably came from their earlier unit record equipment, which used punched cards as input, storage, and output. Since punched cards were (sort of) directly human readable, it was natural to use big endian.
Also, making punch cards bid-endian meant that BCD integers sorted the same way lexographically and numerically, so there wasn't any special sorting mode necessary for numeric fields in punch card sorting machines.
Yes, their choice of big endian probably came from their earlier unit record equipment, which used punched cards as input, storage, and output. Since punched cards were (sort of) directly human readable, it was natural to use big endian.