security blanket 
noun
1A familiar blanket or other piece of soft fabric held by a young child as a source of comfort: my daughter’s three and a half and she’s had a security blanket since she was a year old...
- The truth is, we never really forget the feeling of comfort that old security blanket gave us against our fears, real and imagined.
- I went and got Paws, my security-bear (I never really had a security blanket, I had Paws).
- Named after the famous Peanuts cartoon strip character, Linus, who was never without his security blanket, the project donates quilts to causes including hospices and womens' refuges.
1.1Something that provides reassurance, support, or a sense of security: investors no longer see gold as a security blanket....
- For most businesses, warehouses full of stuff are a kind of security blanket.
- Now cash is one of the few security blankets for wary CFOs.
- The backup is more of a security blanket.
2British A set of security measures or sanctions, typically imposed in order to maintain complete secrecy about something: the size of the Regular Army is under a security blanket...
- The investigative team used the national security blanket to keep everything under wraps.
- This weekend, the capital is under a tight security blanket.
- Despite the intense security blanket, a little has leaked out about the fate of the four survivors.