| |||
under lock and key (The reliefs were discovered in 1962 but have been kept under lock and key ever since and have never gone on public display before. ArcticFox); behind seven seals (locked behind seven seals Alexander Demidov) | |||
be inaccessible to like a sealed book | |||
top-secret |
за семью печатями: 21 phrases in 6 subjects |
Bible | 2 |
Bookish / literary | 1 |
General | 12 |
Idiomatic | 3 |
Informal | 2 |
Makarov | 1 |