Keeping with the Muckle Mickel Michael theme there is of course another place which is apparently definitely named from Norse. Muckle Flugga.

The name comes from Old Norse, Mikla Flugey, meaning "large steep-sided island".
Its geological history is interesting. It's another place that was formed when two giants, Hema and Saxa fought each other for the attentions of a local mermaid by throwing rocks at each other. The mermaid agreed to marry one of them if they could follow her to the north pole. Unfortunately they drowned as neither of them could swim.
https://en.wikipedia.org/wiki/Muckle_FluggaWell, that's the science lesson over.
If we apply Mikla and its variants to the Michael Line we could say that it is the Great Line or Mickle Line rather than the archangel Michael's line.
As a great line it will have had rest stops or way stations were drovers and other travellers could rest. These would no doubt consist of buildings where refreshments could be bought and possible a bed for the night. All such stops indicate their existence by visual signs. What better than a large cross of wood on the roof or gable end. This could also serve as a lightning conductor.
Perhaps to make it more certain that it was a rest stop and not the HQ of the local cattle rustlers' society they could have interwoven the sinuous shape of the track itself on the cross, like a snake perhaps.
They wouldn't have called the track a line of course. That would have been for the railways. Street would have been a much better word. And it exists in all sorts of languages and is all over the place in ancient history.
So Mickle Street is the big street leading from one side of the country to the other.
Just to confirm the pit stop really was what it was they could have written the name on a nearby stone or post. They would keep it simple as people may not have been able to read. So 'street' would have been shortened to its visual elements. 'ST'. So Mickle Street becomes Mickel St with the S still intertwined with the T. Later to be separated for ease of carving. Or perhaps St Mickel, which becomes the name given to the wayside inns.
'Just follow St Mickel and you'll be there in about ten days if you get a move on' could have been the basic instructions given at either end of the street.