Per this article, it was one of the songs from Crescent inspired by poetry Coltrane was reading at the time.  https://www.everythingjazz.com/story/john-coltranes-criminally-underrated-record/  

I've been thinking about just who is Lonnie from Trane's "Lonnie's Lament."  Of course, these days one tries AI.  The answer there is that it is Dr. Lonnie Smith, which strikes me as extremely unlikely.  Smith would have been only 22 when the song was recorded, and the piece has a feel that is like nothing you would find in Lonnie Smith's work (or just about any organist). Yes, Smith later recorded a Trane tribute record.  But I don't think Coltrane wrote a tribute to him. So who is Lonnie?  

Hey.

One of my favorites! But I am a huge listener when Sonny reinventes himself. RCA, Impulse!, Contemporary too! Beastie Boys sampling Jeremy Steig brought him out of the dust! 

Not sure this got a mention, a favorite of mine: