basilisk (n.) Look up basilisk at Dictionary.com
c.1300, from Latin basiliscus, from Greek basiliskos "little king," diminutive of basileus "king" (see Basil); said by Pliny to have been so called because of a crest or spot on its head resembling a crown.
The basilisk has since the fourteenth century been confused with the Cockatrice, and the subject is now a complicated one. [T.H. White, "The Bestiary. A Book of Beasts," 1954]
Its breath and glance were said to be fatal. The South American lizard so called (1813) because it, like the mythical beast, has a crest. Also used of a type of large cannon, throwing shot of 200 lb., from 1540s.