strengthen

verb6

1. •
   To make strong or stronger; to add strength to; to increase the strength of; to fortify.

   • Let noble Warwick, Cobham, and the rest,[…] With powerful policy strengthen themselves. — 1596
2. •
   To augment; to improve; to intensify.
3. •
   To reinforce, to add to, to support (someone or something)

   • Each half-section of the battery weighs about eight tons, and the two underframes had to be strengthened to take this weight. — 1958
4. •
   To grow strong or stronger.

   • my affection seems so superfluous that I often wonder why it should be so strong. But wise or foolish, there it is, strengthening with the years whether I will or no — 1914
5. •
   To substantiate; to corroborate (a belief, argument, etc.)
6. •
   To empower; to give moral strength to; to encourage; to enhearten.

   • Charge Joshua, and encourage him, and strengthen him. — 1611