A farthingale was a conical hoop skirt worn under gowns in the 16th century. It was invented by the Spanish & is commonly thought to have been brought to England by Katherine of Aragon, though apparently she didn't wear it much while she was there. Her daughter, Mary I, did wear them, as did Elizabeth I. Check out this Tudor family portrait for an idea: https://www.rmg.co.uk/stories/topics/mary-i-facts-myths
The farthingale sleeve served as the support for these big poofy leg-o'-mutton sleeves worn by the well-heeled towards the latter part of the 1500s. Elizabeth I is wearing a set in the Ditchley Portrait. She's also wearing a French or drum farthingale, so named because it made the wearer look as if they were standing in a drum. https://www.npg.org.uk/collections/search/portrait/mw02079/Queen-Elizabeth-I-The-Ditchley-portrait
And speaking of the Ditchley Portrait, in 2022 an original showed up in an episode of 'Antiques Roadshow' in a small collection of Elizabethan textiles, along with the sleeve is likely supported, and some linens made by the queen and her ladies. The sleeve may have been the one worn in the famous portrait. https://www.bbc.com/mediacentre/bbcstudios/2022/unique-500-year-old-tudor-sleeve-and-textiles-made-by-queen-elizabeth-i-turn-up-at-antiques-roadshow-in-nottingham
On a tangential note, I personally find late Tudor fashion to be a study in contrasts. On the one hand, the materials used to make them were stunning: the jewels & pearls to decorate them, the silk velvets & rich fabrics, the intricate embroidery, the color palettes - absolutely sumptuous & beautiful.
& then they have to go & ruin it by making people look like they're standing in a drum.
The construction is elaborate - it's like applied engineering, the way so much Tudor clothing was built. And it looks absolutely ridiculous. I mean that drum thing is bad enough, but then there were those massive poofy sleeves & the enormous ruffs that just got wider & wider & wider until they needed their own frames for support... utterly laughable. Reminds me of this: https://www.youtube.com/watch?v=eej3_Zn8bD8
Portrait is about a quarter of the way down the page in that link.