开心锁

Traditional (Taiwan): 開心鎖

kāixīnsuǒ ㄎㄞ ㄒㄧㄣ ㄙㄨㄛˇ

    • to relieve someone's worries or mental block by talking with them

Character by character

Saying俗语俗語

Idiom惯用语 · Rarely used now

Literally
unlock a heart-lock
Meaning
To resolve someone's worries or mental block through talking with them. Warm, approving.

Sources