The story that it comes from the song  Green Grow the Lilacs,  said to have been sung at San Jacinto, is an example of folk etymology.
( ( ( The story ) ( that ( it ( ( comes ( from ( the ( song ( Green Grow ) ) ) ) ) ( ( ( ( the Lilacs ) , ) ( said ( to ( have ( been ( sung ( at ( San Jacinto ) ) ) ) ) ) ) ) , ) ) ) ) ) ( ( is ( ( an example ) ( of ( folk etymology ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN story)) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ comes) (PP (IN from) (NP (DT the) (NN song) (NNP Green) (NNP Grow))) (NP (NP (DT the) (NNPS Lilacs)) (, ,) (VP (VBN said) (S (VP (TO to) (VP (VB have) (VP (VBN been) (VP (VBN sung) (PP (IN at) (NP (NNP San) (NNP Jacinto))))))))) (, ,)))))) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (NN folk) (NN etymology))))) (. .)))
The song Green Grow the Lilacs is an example of modern songs
( ( The ( song ( Green Grow ) ) ) ( ( the Lilacs ) ( is ( ( an example ) ( of ( modern songs ) ) ) ) ) )
(ROOT (FRAG (NP (NP (DT The) (NN song) (NNP Green) (NNP Grow)) (SBAR (S (NP (DT the) (NNPS Lilacs)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (JJ modern) (NNS songs))))))))))