1.
If someone dredges up a piece of information they learned a long time ago, or if they dredge up a distant memory, they manage to remember it.
...an American trying to dredge up some French or German learned in high school...
PHRASAL VERB : V P n (not pron)
2.
If someone dredges up a damaging or upsetting fact about your past, they remind you of it or tell other people about it.
I wouldn’t want to dredge up the past...
It’s the media who keep dredging it up.
PHRASAL VERB : V P n (not pron) , V n P