teeter (v.)

1843, "to seesaw," alteration of Middle English titter "move unsteadily," probably from a Scandinavian source akin to Old Norse titra "to shake, shiver, totter, tremble," from Proto-Germanic *ti-tra- (source also of German zittern "to tremble"). Meaning "move unsteadily, be on the edge of imbalance" is from 1844.

Noun teeter-totter "see-saw" is attested from 1871 (earlier simply teeter, 1855, and titter-totter in same sense is from 1520s). Totter (n.) "board swing" is recorded from late 14c.; see totter (v.), and compare see-saw.

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Definitions of teeter from WordNet
teeter (v.)
move unsteadily, with a rocking motion;
Synonyms: seesaw / totter
teeter (n.)
a plaything consisting of a board balanced on a fulcrum; the board is ridden up and down by children at either end;
Synonyms: seesaw / teeter-totter / teetertotter / teeterboard / tilting board / dandle board