Acquaintances or past friends.

Songs

Computer passwords....because they're ALL the same! ha ha kidding

Telephone numbers.

Times that they were insulted by relatives.

I think it is songs too

Faces, I never forget a face.

According to 'Seven Little Words', swan offspring are called 'cygnets'.

Dumb little trivia facts that have no use.

Faces.

Good deeds.

Rusty

My first thought was phone numbers also.

I think it's odors, so many of them can bring a recall of a past event.

Words in their native language ?

first names?

I thought baby swans were cygnets. Interesting.

They are cygnets. But they have other names/synonyms too.

Swear words!

:)

Remembering 5,000 of anything by the average person is a great question. i'll agree it is smells and odors too.

words in general ... and 5k would be a tiny vocabulary