Webster's Revised Unabridged Dictionary · 1913

Kneel

Kneel (nēl) , intransitive verb

[Old English knelen, cneolien; akin to Dutch knielen, Danish knale. See Knee.]

To bend the knee; to fall or rest on the knees; -- sometimes with down.
And he kneeled down, and cried with a loud voice, Lord, lay not this sin to their charge. — Acts vii. 60
As soon as you are dressed, kneel and say the Lord's Prayer. — Jer. Taylor

The act of kneeling, when performed in front of a person, is often done as a sign of respect, humility, or supplication. It has a similar significance when performed in front of religious objects, such as an altar or shrine.