From secure +‎ -ment.

securement (plural securements)

1. The act of securing.

   a wheelchair securement device used on a bus

   • 1673, Elisha Coles, A Practical Discourse of God’s Sovereignty, London: J. Murgatroyd, 1794, “Of Perseverance,” pp. 367-367,^[1]

     In the tenth of John, our Saviour says, his “sheep shall never perish,” ver. 28. which is, in effect, their faith shall never fail; for, safe they cannot be from perishing, without the securement of their faith.

   • 1866, Samuel Shellabarger, addressing the Civil Rights Bill in the House of Representatives, cited in William H. Barnes, History of the Thirty-Ninth Congress of the United States, New York: Harper, Chapter 10,^[2]

     Now, sir, can this Government do this? Can it prevent one race of free citizens from being by State laws deprived as a race of all the civil rights for the securement of which his Government was created, and which are the only considerations the Government renders to him for the Federal allegiance which he renders?