Probably an elaboration of Lily, or a form of Elizabeth — lily. One of the top ten American girls' names of the 1900s, back in the top hundred since 2002.
Lillian ranks 57th among American girls in 2025, with 3,966 born that year. Its best year was 1920, when 10,075 babies were given the name, ranking 18th. The typical living American called Lillian is about 20 years old today. It is relatively most common in Vermont, where it accounts for 0.55% of births.
Source: US Social Security Administration, national and state name files, 2025 release, and the Office for National Statistics for England and Wales. Etymology researched and written by our editors. Living-population and median-age figures are our own estimates, described in the methodology.