up one's sleeve

English

From the practice of magicians hiding tricks or gimmicks in the sleeve.

(idiomatic) Hidden and ready to be produced as needed; in reserve.
I have tried everything I can think of, and I don't have anything more up my sleeve.
- 1922, Agatha Christie, “Chapter 16”, in The Secret Adversary:
  "There may be things that you know which I do not. I have not pretended to be aware of all the details of your show. But equally I've got something up my sleeve that you don't know about. And that's where I mean to score. Danvers was a damned clever fellow——" He broke off as if he had said too much.

In this sense, the phrase most commonly occurs after a nominal such as ace, trick, surprise, something, more, nothing, anything.

hidden, in reserve

Arabic: please add this translation if you can
Chinese:
Mandarin: 锦囊妙计 (zh) (jǐnnángmiàojì)
Finnish: hihassa
French: dans sa manche
German: im Ärmel
Icelandic: luma á (verb), eiga í pokahorninu (verb), lúra á (verb), hafa í bakhöndinni (verb)
Italian: avere un asso nella manica
Japanese: please add this translation if you can
Korean: please add this translation if you can
Polish: w rękawie, w zanadrzu
Portuguese: na manga
Russian: за па́зухой (ru) (za pázuxoj), исподтишка́ (ru) (ispodtišká) (secretly)
Spanish: debajo de la manga