LSJ
τά, tumbling or diving tricks, Hsch. (s.v.l.).
(Acc. to D.H. ap. Et. Gen., from ἀρήν, one that plunges and butts like a lamb; but rather from ἀρνεύω butt or dive headlong like a ram (ἀρνεύς, cf. ἀρνειός).)
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)