[noaoh]

I was thinking of putting my social security card + the master password to my bitwarden account in a safe deposit box. Good to know that's not a good idea.

[Obscurity4340]

Just spend a few hours making and scattering "horcruxes".

[OJFord]

Shamir secret sharing is a rigorous way to do it. Maybe for this purpose just spreading catenable chunks and some duplicates would be fine though.

(It would 'just' mean one being discovered weakens the overall password, if the finder knows what it is. With SSS knowing any less than all of the shares doesn't reveal any part of the secret.)

[Snawoot]

Well-known implementation of SSS: https://linux.die.net/man/1/ssss-split

[ghaff]

I haven't had a physical social security card since a wallet was stolen 40+ years ago and I've never needed it.

And there are various approaches to safeguarding passwords that don't involve writing it down in one place.