From 身(み) (mi, “body”) + 投(な)げ (nage, “throwing”, 連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 投(な)げる (nageru, “to throw”).). Literally, "throwing one's body".
身(み)投(な)げ • (minage)