The hysteron proteron ("latter before") is a rhetorical device in which the first key word of the idea refers to something that happens temporally later than the second key word. The goal is to call attention to the more important idea by placing it first.
The standard example comes from the Aeneid of Virgil, Moriamur, et in media arma ruamus, or "let us die, and charge into the thick of the fight" (ii. 353). Another example is from the Last Supper, where Jesus tells his disciples "Take, eat; this is my body."
