The compound 'twenty-odd' follows a long-standing English pattern for forming approximate numbers, combining a cardinal number with the adjective 'odd'. The word 'twenty' originates from the Old English 'twēntig', a compound of 'twēgen' (two) and '-tig' (group of ten), literally meaning 'two tens'. 'Odd' entered English from Old Norse 'oddi', initially denoting a triangle or a point, which metaphorically extended to mean an uneven number or a surplus item that does not form a complete pair. By the late 16th century, this sense of surplus was applied after numbers to signify 'and a bit more', creating a concise way to express a rough estimate slightly above a round figure.

Structure: twenty (number) + odd (extra, not even) - twenty: From Old English twēntig, meaning 'two tens'. Its functional role is to specify the base number. - odd: From Old Norse oddi, meaning 'point of land, triangle', later 'third or unmatched number', evolving to mean 'left over, extra'. Its functional role is to indicate an indefinite, small surplus beyond the base number.