This pet form of Helena and other ena-ending names, long used as an independent name, is attracting notice again as an option both multicultural and simple. Lena was a Top 100 name from 1880 to 1920. It reached its highest ranking since the Truman Administration in 2015 at Number 272, and has dropped only slightly to 276 in 2016.
A past inspiration might be the lovely singer Lena Horne, a contemporary one is the hot creator of and actress in Girls, Lena Dunham, another might be Game of Thrones actress Lena Headey.
Lena Grove is a simple but strong character in William Faulkner's Light in August.