Subarmalis or gambeson?

[Atawulf]

As I recall, gambesons are more associated with knightly armors, like hauberks and Renaissance plate armors.

Aketons and pourpoints were worn under mail. Arming doublets were worn under plate. They don't have much in common with each other. Gambesons were different again - they were a lot heavier and thicker and meant to be worn by themselves like a linothorax or padded jack. A lot of earlier plate didn't need anything because it had a padded liner. It could be worn over regular clothing. IMO Roman mail had an integrated padded liner too. So did scale armour.

So, in your oppinion what is the most accurate garment to wear under armour in this age (5th and 6 th centuries)?