Archaic noun (reading: おと): a younger brother as referred to by an older brother — an old-fashioned term corresponding to modern 'otōto' (younger brother) found in classical texts.
古い物語では、兄が『おと』を守る場面がよく描かれる。
In old tales, scenes of an older brother protecting his 'oto' are often depicted.
彼は兄にとって大切な『おと』だった。
He was an important 'oto' to his older brother.
Archaic noun: the youngest child of a family (the youngest offspring). This use is largely obsolete in modern Japanese.
昔の記録には『家の弟（おと）は病弱であった』とある。
An old record says, 'the family's youngest child (oto) was frail.'
Archaic prefix: used as 'oto-' to mean 'young,' 'younger,' or 'youngest' in compounds. This prefix usage is mostly obsolete today.
古文では『おとむすめ』のように若さを表す語が見られる（現代語では稀）。
In classical texts you can find words like 'oto-musume' that express youth (rare in modern language).
Archaic prefix: 'oto-' carrying connotations of 'young and beautiful' or 'cute'. It appears in literary or poetic contexts but is largely obsolete in modern usage.
古い歌や詩では、『おと』の付く語が女性の愛らしさを褒めるために使われることがある。
In old songs and poems, words with the prefix 'oto-' are sometimes used to praise a woman's charm.