Hardening \Hard"en*ing\, n.

1. Making hard or harder.

2. That which hardens, as a material used for converting the surface of iron into steel.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Harden \Hard"en\, v. t. [imp. & p. p. Hardened; p. pr. & vb. n. Hardening.]

[OE. hardnen, hardenen.]

1. To make hard or harder; to make firm or compact; to indurate; as, to harden clay or iron.

2. To accustom by labor or suffering to endure with constancy; to strengthen; to stiffen; to inure; also, to confirm in wickedness or shame; to make unimpressionable. ``Harden not your heart.'' --Ps. xcv. 8.

I would harden myself in sorrow. --Job vi. 10.

Source: Webster's Revised Unabridged Dictionary (1913)