(Uso kara deta makoto;
“Truth that came from a lie”)
Something that was said as a lie or joke turns out to be true after all. Note that this applies to coincidences and accidental truths, not “fake it ‘til you make it” type situations where the truth is produced from the lie per se. A familiar example might be the boy who cried wolf: the wolf eventually arriving is an ironic turn, not a natural consequence of the boy lying.
This noun phrase centers on the noun 実 (makoto), “truth,” modified by the verb 出る (deru), “to go out,” in past prenominal from. The particle から (kara), “from” marks the starting point of this verb of motion; in this case the noun 嘘 (uso), “untruth.”
This is the う (u) entry of the Edo iroha karuta set.
One variant uses the more archaic particle より (yori) in place of から. It is also possible to replace the character 実 (which can also mean “fruit”) with other characters that can also mean “truth,” 真 or 誠, without changing the phrase’s meaning or pronunciation.
Compare and contrast 瓢箪から駒が出る.
(“Kodomo no toki no kenka de, shourai, sekaiteki ni yuumei na kagakusha ni natte miseru! to ka itta koto ga atta kedo, kyou, kono shou wo hontou ni ukeru nante, uso kara deta makoto de imadani hanshin hangi da.”)
[“When I was a kid, sometimes during a fight I’d say stuff like I’ll show you by becoming a world-famous scientist some day!, and stuff like that. But today, actually receiving this award, I can only half believe that that lie actually came true.”]