Hi there.
I currently do English Literature, History (Medieval and Tudor), Classical Civilisation, Physics, with GCSE Astronomy and Ancient Greek.
The etymology of words is always very interesting, and if you're interested in it, I'd suggest Class Civ over History, because you learn numerous Latin phrases (though this might be determined by what course you'll do. There are 13 different AS courses, and I currently do Cicero: Life and Times, and The Odyssey by Homer) without having to learn huge clumps, and I've found so far that I've learnt many things that can also apply to my other subjects.
However, I'm leaning more towards History suggestion wise. Though both are respected A-Levels for pretty much ALL humanities subjects at university, History can lead into so many different subjects further on in life and, if you're worried about the sources, you have two source questions, 20 marks and 40 marks, and they're an extension of what you do at GCSE. You don't have to be good at GCSE History, though it might help, as the person who got the lowest GCSE mark in my A Level class is definitely finding it the hardest... but you can't let GCSE put you off! Try looking at some exam papers and some of the wider reading for History before you make your choices, and I can highly suggest reading around Classical Civilisation too.
If it's the essays that concern you, remember: the humanities ARE essay writing, and if you're good at it, your A Levels will be enjoyable and you'll learn to curb your writing style too, and to be able to write in numerous styles is a great skill if you're interested in the humanities. I took Physics to break up the essay writing, but I've now found myself wanting to drop it after AS and I can't way to just write essays! Also, with History GCSE, you're not near your exams yet and you'll be surprised how much you can improve your essay writing/source analysis with practise, and this is what I suggest: practise for history is the key!
Good luck with whatever you choose!