chicken out of something doing something

Từ điển Oxford Advanced Learner 8th

ˌchicken ˈout (of sth/of doing sth) derived
(informal)to decide not to do sth because you are afraid
•You're not going to chicken out, are you?
•Kim put my name down for a sponsored parachute jump but I chickened out at the last moment.
Main entry: ↑chicken_derived