Darling or dear one
Darlen is a modern variation of the English word 'darling', used as a term of endearment. It likely emerged as a phonetic variant of Darlene, which gained popularity in the early 20th century. The name conveys a sense of affection and being cherished.
Less common today
Darlen isn't in the latest US Top 1000. It last peaked at #10,163 in 2008.
US births per 5-year period, 1990βpresent (SSA data).