Stiffen (verb)

1. Make or become stiff or stiffer.
2. Make or become more formal or formalized.

Origin:

From old english stīfian, of germanic origin; related to dutch stijven and german steifen.

Examples:

1. The dough needs to be kneaded until it stiffens.
2. She stiffened her resolve to finish the race.
3. The air was so cold that the paint stiffened on the brush.
4. His spine stiffened as he heard the bad news.
5. The company's policies have stiffened over the years.