Meaning of “stir sth up” - Learner’s Dictionary

stir sth up

phrasal verb with stir us uk /stɜːr/ verb present participle stirring, past tense and past participle stirred

to cause arguments or bad feelings between people, often intentionally:

I think she just likes to stir up trouble.

If something stirs up memories, it makes you remember events in the past:

(Definition of “stir sth up” from the Cambridge Learner’s Dictionary © Cambridge University Press)