LOL, Back in the day, me and my buddies used to do our fair share of examining and eye balling the women, and then talking, and sharing our observations and opinions.

I used to refer to the small Asian ladies as keys, like having them get on top, and while riding me CG, to turn on my pole, hence like a key turning in a keyway.

Then came TER, and a new term, Spinner, which I concluded, was meant as the same action as a Keyer, Mount up on the pole, and Spin around to various positions.

So the term Spinner, more than likely, coined
by an individual, who was talking to his buddies,
and said, I seen this small slender woman, " Spinner" with
whom I imagined had mounted me CG and Spun around
on my pole, and Keyed me! LOL

... based on looking at your reviews:  Ava and Jillian.  The thing about them is, they don't just exude the personality, maturity, and experience of many of our great 40+ providers... they ARE great 40+ providers!  

...this is the most probable origin of the term spinner:

http://www.urbandictionary.com/define.php?term=Thai+Basket

Most people define a spinner as a woman less than average height ( less than 5'5") and who weighs around 100 # but 115 # or less. That would make it easy for most men to be able to manipulate the basket up and down and be able to spin it slowly. I've heard some say that a spinner should also be less than a 34C but I would never discriminate against a spinner for having larger breasts...that just wouldn't be right.  ;

http://www.urbandictionary.com/define.php?term=spinn

I first heard the term when I was stationed in Thailand in the 70s.  Although I visited Thai massage parlors (but never in Bangkok) and ran the bars for my share of bargirls (in several Thai cities, including Bangkok -- and massage ladies often ran the bars after their shifts), I never heard of, let alone saw, ladies in spinning baskets.

However, a common expression among servicemen in Thailand was to say that a lady enjoyed doing "sit spins" on one's penis (that is, cowgirl, be it regular, Asian or reverse.)  Such a girl was known as a spinner.  Since nearly all Thai ladies were petite by U.S. standards, the term was not primarily used to identify smallish, petite ladies -- as we used it in Thailand, it typically meant a younger, energetic or playful lady who especially enjoyed doing cowgirl.

was in the novel "Shaft," published in 1970.  But I can't prove it was the first use of the term ever, just the first time I heard it.