Words hardly used now

Swinging has a more precise meaning now:-)

Flibbertigibbet
Floozie (my favourite!)
Ragamuffin
Rapscallion
Blithering (idiot)

Groovy.
It's a gas.
Hunky dory

May I recommend the podcast "Something rhymes with Purple"?

It contains Gyles Brandreth who can be rather polarising so not for everyone. He and Susie Dent discuss words and their origins and try to revive near-obsolete ones.

My father used all of these.

Fewer.

Witzend

Flibbertigibbet
Floozie (my favourite!)
Ragamuffin
Rapscallion
Blithering (idiot)

These.

Blithering idiot was one of my dad’s favourites too.
Golly (golly gosh)
Hip
Whoopsadaisy

'By Jove'!

Toodle pip! (Though still sufficiently known to feature in a crossword the other day!)

fetch
this is in danger of dying out.
some younger people literally do not know what it means.
so i try to keep it in circulation by using it whenever possible.
americans do not seem to use the word, surprise.
they are only shocked by everything, including pleasant or quite ordinary events.
until i realised this i used to be puzzled by some youtube titles.

Ripping!
(Mostly seen in old fiction for boys. ‘I say, Carruthers, what a ripping wheeze!’😂)

Gordon / Gawd n Bennett.

U and non-u.

Mamie

Gordon / Gawd n Bennett.

Still used in our house😁 Gawdon Bennett. Words that you don’t hear:
Tip top
Beano ( a party or bunfight)
Bunfight! ( kids tea party)
Madam ( in shops)😄

The fat boy of the Remove (from Billy Bunter). I don’t think you are supposed to say ‘fat’ now 😏

Discombobulated

It's magic?
Fab.
Just the ticket.
You're such a card.
Right on, man.
Trendy.

Oh my giddy aunt
How very dare you
Impertinent
Above your station
Mollycoddle
Twerp
Lollygag
Dawdle
Mithered

Charabanc
Browned off
Brassiere
Scullery

Ne’er do well
Yob

Nice one, Cyril!
Singlet.
Eiderdown.
Bedspread.

Smithereens.

blimey cricky

Collywobbles.