OK sign
/(ˌ)əʊˈkeɪ ˌsʌɪn/originally and chiefly US
noun
A mark of ‘OK’, or other sign indicating that something is satisfactory; specifically a gesture made by forming the thumb and index finger into a circle with the remaining fingers raised and spread, signifying understanding, agreement, approval, etc., or that the signaller is all right.
Origin
1920s; earliest use found in Hart Crane (1899–1932), poet. From OK int.1 n.2adverb + sign.