formal or literaryusually written using kana alone
Formal or literary rhetorical question word meaning 'how' or 'why'. Used in classical or highly formal contexts to express doubt or negation. Often appears in set phrases like いずくんぞ知らんや (how could one know?).
なぜ is the standard modern word for 'why'. いずくんぞ carries a stronger rhetorical, classical tone.
Etymology
Derived from classical Japanese いずく (where) + ん (hypothetical/volitional auxiliary) + ぞ (emphatic particle). The kanji forms are ateji (phonetic equivalents) and not related to the meaning.
