|Definition - A Late Latin rhetorical term denoting a rapid transition from one subject to another.|
Etymology - The term derives from the Greek metastasis, transference, removal, or change.
Oxford English Dictionary - Its first citation is from 1586:
"Metastasis or Transitio, when in briefe words we passe from one thing to another."
(A. Day Eng. Secretary ii. (1625) 96)