Some of us knew the word "tiovivo" from international TV or literature, but I've never heard it used in daily speech in Mexico.
As for "ferris wheel", in Mexico that's a "rueda de la fortuna". Not sure why.
Finally, in my little Facebook poll, most of my friends said the thing is called "volantín", so I guess that's the name, and "ola" could have been a local nickname.
