I had another look at the actual article/RFC: This is more than just the little endian/big endian byte order, it's about the bit order of serial messages, where, unlike bytes, the bit order could actually be different (for bytes stored in memory the bits of each individual byte in modern / semi-modern computers are always stored in the same order whether it's a LE or a BE memory architecture). In a serial protocol you could send the most significant bit of the stream first, or the least significant bit first, and that's what's at first discussed in that RFC.