'midmost' originates from Old English, specifically the word 'midmest', where 'mid' meant 'middle' and '-mest' was a superlative suffix meaning 'most'.

'midmost' changed from the Old English word 'midmest' and eventually became the modern English word 'midmost'.

Initially, it meant 'the most middle' or 'the very center', and this meaning has largely remained the same in modern usage.