thaw out
US /θɔː aʊt/
UK /θɔː aʊt/

1.
2.
to become more relaxed, friendly, or less reserved
:
•
After a few drinks, he started to thaw out and tell jokes.
•
The new student was shy at first, but she quickly thawed out with her classmates.
to become more relaxed, friendly, or less reserved