Initials for Little Junior or a combination of names.
Lj is a modern initial-based name typically used as a nickname for a son who shares his father's name (Little Junior). It can also serve as a phonetic shortening for any first and middle name combination starting with L and J, such as Liam James or Lucas Jude.
Less common today
Lj isn't in the latest US Top 1000. It last peaked at #6,317 in 2007.
NFL linebacker
NFL defensive end
Author of The Vampire Diaries series
US births per 5-year period, 1990βpresent (SSA data).