Words related to -en
c. 1300, quikenen, "come to life, receive life," also transitive, "give life to," also "return to life from the dead;" see quick (adj.) + -en (1). The earlier verb was simply quick (c. 1200, from late Old English gecwician, and compare Old Norse kvikna).
The sense of "hasten, accelerate, impart speed to" is from 1620s. The intransitive meaning "become faster or more active" is by 1805. Also, of a woman, "enter that state of pregnancy in which the child gives indications of life;" of a child, "begin to manifest signs of life in the womb" (usually about the 18th week of pregnancy); probably originally in reference to the child but reversed and also used of the mother. Related: Quickened; quickening.
1560s, of fruits, seeds, etc., "grow ripe, come to maturity," from ripe (adj.) + -en (1). Figurative use by c. 1600. The transitive sense of "bring to maturity, make ripe" also is from 1560s. Related: Ripened; ripening. The earlier verb was simply ripe, Middle English ripen, from late Old English ripian, from the adjective.
"to make sorrowful," 1620s, from sad (adj.) + -en (1); earlier "to make solid or firm" (c. 1600). The earlier verb was simply sad, from Middle English saden "become weary or indifferent," also "make (something) hard or stiff," from Old English sadian, which also could be the source of the modern verb. The intransitive meaning "to become sorrowful" is from 1718. Related: Saddened; saddening.
late 14c., sharpenen, "intensify;" mid-15c., "make a point sharp or sharper," from sharp (adj.) + -en (1). Related: Sharpened; sharpening. The older verb was simply sharp (Middle English sharpen), from the adjective and partly from Old English gescirpan (West Saxon), scerpan (Anglian) "to score, scarify;" also compare scearpung "scarifying."
To sharpen (one's) pencil in the figurative sense of "prepare to get to work" is by 1957, American English.