Then prepare to have your mind blown (if you haven't heard about this before): the correct culture-agnostic term is "grouping separator" because not everyone us

Then prepare to have your mind blown (if you haven't heard about this before): the correct culture-agnostic term is "grouping separator" because not everyone uses 3 digit groups - in some East Asian languages (specifically Japan and China, not sure who else) you have separate words for "ten thousand" and use 4 digit groups.