means To move back and forth or in a curve from a fixed point, or the seat suspended by ropes or chains that lets you do exactly that.

from From Old English 'swingan,' meaning to beat, strike, or flog — a word about violent motion, related to German 'schwingen,' to brandish or wave. The sense slowly softened from striking the air to moving freely through it, and by later centuries the gentle suspended seat we know had borrowed the name. The musical 'swing,' that lilting rhythmic lean, came much later, but it kept the same heart: the pull of something moving with momentum.