pre-noun adjectival
Expresses surprise or disbelief at an unforeseen situation; often used in phrases like とんだことになった (things took an unexpected turn).
とんだところで彼に会った。
I ran into him in an unexpected place.
とんだ災難だった。
It was an unexpected disaster.
pre-noun adjectival
Used to emphasize how bad or serious something is; often carries a nuance of exasperation or strong negative evaluation.
とんだ目に遭った。
I had a terrible experience.
とんだ嘘をつくものだ。
What an outrageous lie to tell.
adverb
Obsolete adverbial use meaning 'very' or 'extremely'; not used in modern Japanese.
古語では「とんだ遠く」のように使われた。
In classical language, it was used as in 'とんだ遠く' (very far).
意外 is a more neutral 'unexpected'; とんだ adds a stronger emotional reaction, often negative.
大変 can mean 'very' or 'terrible', but is more versatile and less emotionally charged than とんだ.
Derived from the verb 飛ぶ (とぶ, 'to fly'), with the past/perfective form 飛んだ (とんだ) taking on a figurative meaning of 'unexpected' or 'outrageous'. The exact semantic shift is uncertain, but it likely developed from the idea of something 'flying' beyond normal bounds.