Oreo
Language changes doesn’t it? The plural in Anglo Saxon times was an ending of en, that changed with the Normans into es plural endings.
So before 1066 a pair of shoes ( as we now call them) was shoen.
All those en plural endings vanished apart from two, oxen and brethren.
Well, the Anglo Saxons were Germanic and the Normans were French Vikings, so I guess they used the plurals they felt happiest with.
We haven't yet decided if we are Roman or British with some words we use. Fora or Forums, Memoranda or Memorandums, Gymnasia or Gymnasiums? As for roofs or rooves, I know rooves has always been the "correct" plural, but I have never felt comfortable with it. However, I will draw the line at horses having hoofs instead of hooves, if and when that becomes an issue. (and it is definitely Elves on shelves).