Look Daggers Meaning

Example : 1835, Washington Irving, Abbotsford and Newstead Abbey, ch. 1:  Before him sat the grim baron, with a face worthy of the father of such a daughter, and looking daggers and ratsbane.1912, Jack London, Smoke Bellew, ch. 2:  Both employers looked daggers at Kit, for the insult rankled.1986, Stephen Coonts, Flight of the Intruder (2006 edition), ISBN 9781591141273, p. 116:  [T]wo hostesses approached and looked daggers at Suzy and Teresa, both of whom glared back.