Everything's a learning experience

One thing the First Reader and I have in common is that, as introverted readers from childhood, each of us has a large vocabulary of words that we know from reading but have never heard or used in conversation. This leads to frequent exchanges like:
"Have you ever heard of X-x-x?"
"Oh, is that how you pronounce it? I always thought it was x-X-x."
"Well... it's how I pronounce it; I haven't a clue what is correct."
Of recent years, it's likely that at least one of us will have a smartphone within reach and we'll figure out the approved pronunciation on the spot. But there's no telling how many Debatable Words remain.
I hadn't expected that knee-surgery-complicated-by-pneumonia would affect this phenomenon, but it's become one of the less boring side effects of the whole thing. For about ten days I felt like a limp dishrag, too tired even to hold a book or a Kindle, and for the first time in my life I've been listening to audiobooks. When in normal health I find them too slow, but for the last week and a half "slow" has matched my comprehension perfectly.
Naturally, I haven't been taking notes and can't tell you which words I've heard out loud for the first time ever. The only ones I remember are the mysteries.
When I read Jane Austen, I see "shew" and hear "show," assuming that spelling but not pronunciation has changed. But whoever read my audiobook of Persuasion consistently read it as "sh-you". Which jarred, but may be correct; I'm too tired to do the research now.
The other surprise came while I was listening to Connie Willis' Blackout. Her characters, stumbling around in the Blitz, frequently encountered "arp wardens" and every time that jarred too. Without thinking about it, I'd always mentally heard "ARP" in this context as "Ay-ar-pee," spelling out the letters instead of pronouncing them as an acronym. Now I wonder which pronunciation the contemps used. That should be discoverable if I dig out enough contemporary radio broadcasts, but I'm not going to do it today. A native speaker of English-English rather than America-English might know; Ashley, if you read this, what's your pronunciation of ARP?