The idea is the secret was explosive because of the surprise it would have created, but the surprise is not necessarily negative. See the following examples:French: explosive discovery of the truth (with risks)
The origin of se ha descubierto el pastel is said to date back to times in which the cake makers (sometimes) didn't insert as much filling as anounced (or any at all) so clients asked them to cut the cake to discover if it had the anounced filling.does the truth taste good???
Interesting. German is more like Italian than Dutch in this regard: die Katze aus dem Sack lassen.Italian: (act., causative) "far uscire il gatto del sacco", just the same as in the other Romanic languages...
Just BTW: we do not have "to let the cat out of the bag", only the (static/dynamic) conclusion: "the cat comes out of the bag". it might be interesting to distinguish them in our answers: causative (let) vs. spontaneous/..."...
I guess it is technically fine in both cases.The idea is the secret was explosive because of the surprise it would have created, but the surprise is not necessarily negative. See the following examples:
Je voulais faire une surprise à ma copine pour son anniversaire et l'inviter au restaurant, mais sa mère a vendu la mèche.
(I wanted to surprise my girlfriend for her birthday and invite her to the restaurant, but her mother let the cat out of the bag)
Les terroristes voulaient commettre un attentat mais leurs complices ont vendu la mèche, et ils ont été arrêtés avant.
(The terrorists wanted to carry out an attack but their accomplices let the cat out of the bag, and they were arrested before they did)
I don't know if the English expression suits in both cases.