expression, noun
what; what sort of thing
Used to ask what someone is referring to, often when the speaker doesn't understand the topic or wants clarification. Common in questions like 何のことですか？
「例の件、どうなった？」「何のことですか？」
"How did that matter turn out?" "What are you talking about?"
expression, noun
something unusual; something out of the ordinary
Used in negative or questioning contexts to indicate that nothing special or unusual is happening. Often appears as 何のこともない or 何のことなく.
一日中、何のこともなく過ぎた。
The whole day passed without anything unusual happening.
interjection
what the heck; holy cow
Exclamatory use expressing surprise, disbelief, or frustration. Often used as a standalone interjection.
何のこと！また遅刻かよ。
What the heck! Late again?
何 is the basic word for 'what', while 何のこと is a phrase meaning 'what (thing/matter)' or 'what are you referring to'.
何事 can mean 'what thing' or 'something unusual', similar to 何のこと, but is more formal and often used in set phrases like 何事もない.
Phrase composed of 何 (what) + の (possessive particle) + こと (thing/matter). The combination is straightforward and has been used in Japanese for centuries.