In SoCal in the early 60s it was “zoris” ( no “e” in there anywhere folks) or “thongs”. I heard some folks use “go-ahead”, but that was weird. Oriental folks (mostly Japanese in those days) said either “slippers” or “zoris”.
“Flip flops” came later; late 70s or so.
The first time I heard the term “shower shoes” was in the military in the 80s and I had no clue what they were talking about.
Flip-flops. Though when I was a kid, my friends and I used ‘sandals’ and ‘flip-flops’ interchangeably. And one family used ‘zoris’; they were in the Foreign Service and away half the time, usually in Europe; I always assumed they picked the term up somewhere else in the world.
Flipflops, or occasionally sandals. I’ve heard them called thongs, though not all that often. I tend to think of sandals as leather (and not thong-style).
I’ve never heard the term “pool shoes” before either, though I have heard of swim shoes. That’s what I’d assume “pool shoes” referred to.
I have heard the term “shower shoes” once or twice but didn’t think what was meant. If I’d thought about it I’d probably have assumed something like what Skywatcher linked to.
I had to google. If you believe Slate, go-ahead was the original term. I’m checking to see if it was a brand name, but I mostly remember them as cheap generics. Nope. No sign that it was ever a brand name.
In my house we called them slippers or flip flops. Thankfully, a couple of years ago I read an article on why they are** bad **for your feet, so I will **NEVER **wear them, except maybe for a few seconds to get from the house to the pool.
I have heard them referred to as “flip flops”.
In my youth I called them thongs or sandals. Come tho think of it, Mother called them thongs the Summer she didn’t buy me tennis shoes because I would need larger shoes for school.
As an adult, I make an effort to not speak of them.