The story
The phrase may have originally been used to qualify a statement of advice, opinion, or suggestion by referring to such a statement and describing it separately from making it.
Etymology from Wiktionary, CC BY-SA 4.0.
for what it's worth
Today it means: Considering what limited worth this advice, opinion, or suggestion might have for you; used to soften the presentation of unsolicited advice or information that may not be relevant. Full definition →