c. 1300, "to make dark;" late 14c., "to become dark," from dark (adj.) + -en (1). The more usual verb in Middle English was simply dark, as it is in Chaucer and Shakespeare, and darken did not predominate until 17c. The Anglo-Saxons also had a verb sweorcan meaning "to grow dark." To darken someone's door (usually with a negative) is attested from 1729.
1. Nothing was going to darken his mood today.
2. The sky began to darken as the storm approached.
3. Please darken the blue paint with black paint.
4. Go ! And never darken my door again!
5. " Clouds darken with darkness of rain, Streams pale with pallor of mist . "