Fixed expression emphasizing that something is exactly that and nothing else, often used before a noun or clause. Similar to 他ならない but slightly more literary.
See also: 他ならない
His success is nothing but the result of hard work.
The one who can solve this problem is none other than you.
Standard kanji spelling.
Rarely used kanji form.
From 他 (ほか, 'other') + ならぬ (archaic negative of なる, 'to be'), literally 'it is not other'. The phrase fossilized as a set expression meaning 'none other than'.