English tricycle comes from French, whose formation combines tri- with Greek kyklos, wheel. The name counts the wheels.
Tri- has both Latin and Greek sources in modern learned formations. Only its numerical meaning is scored here; the complete vehicle name is not an ancient Greek borrowing.
Sources
- Merriam-Webster: tricycle
Word History supplies the French formation and Greek kyklos, wheel.
- Merriam-Webster: tri-
Combining-form sense 1 supplies three and the trigraph example; Word History records Latin and Greek sources.
- Online Etymology Dictionary: cycle
Also from Greek *kyklos* “circle, wheel”: cycle, bicycle
- Online Etymology Dictionary · tri
Meanings of the older forms on the word path.