This one's for Maurice - thanks for the request!
I explained this to Caron's Level 4 class last week, I believe, when I was substituting.
The Hebrew word for bicycle is אוֹפַנַּים (oh-fah-NAH-yeem).
While Modern Hebrew (going on Medieval) renders a wheel a גַּלְגָּל (gahl-GAHL), the Biblical Hebrew word for wheel is אוֹפַן (oh-FAHN). The יִים- (AH-yeem) ending on a noun doubles the noun - so that אופן (a wheel) becomes אופניים (a double wheel... or two wheels)... like this one: