ETYM Latin catapulta, Greek, prob. from kata down + pallein to shake, hurl.
1. Y-shaped stick with elastic between the arms; used to propel small stones; SYN. sling, slingshot.
2. An ancient heavy war engine for hurling large stones; SYN. bricole, onager.
3. Launches aircraft from a warship; SYN. launcher.

ETYM Probably a reduplication of saw, to express the alternate motion to and fro, as in the act of sawing.
A plaything that is ridden up and down by children at either end; SYN. teeter-toter, teeterboard.