strengthen

Etymology

From rare Middle English strengthenen (14th c.), from earlier strengthen (12th c.), where -en is the infinitive ending. Probably the original form was reinterpreted as strength + -en around the time when the infinitive ending was being apocopated in late Middle English.

verb

1. (transitive) To make strong or stronger; to add strength to; to increase the strength of; to fortify.
   strengthen a muscle
   strengthen a wall
   strengthen one's willpower
   strengthen one's authority
   A little hardship, and a little struggling with the rougher elements of life, will perchance but strengthen and increase his courage, and prepare him for the conflicts and struggles of after years. 1851, anonymous author, Arthur Hamilton, and His Dog
2. (transitive) To empower; to give moral strength to; to encourage; to enhearten.
   my father and mother strengthened me in this my first impression, saying in my presence, I was intended for some great purpose 1831, Nat Turner, The Confessions of Nat Turner
3. (transitive) To augment; to improve; to intensify.
4. (transitive) To reinforce, to add to, to support (someone or something)
   strengthen an army
5. (transitive) To substantiate; to corroborate (a belief, argument, etc.)
   strengthen the cause
6. (intransitive) 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, Elizabeth Robins Pennell, Our Philadelphia