Question: Effie Crockett is credited with creating the song that was based on what English ballad?

Context articles: Robin Hood and Allan-a-Dale
The Knight and the Shepherd's Daughter
Now (The Dubliners album)
The Beggar-Laddie
King Arthur and King Cornwall
The Unquiet Grave
The World Turned Upside Down
Rock-a-bye Baby
Effie Crockett
No Man's Land (Eric Bogle song)

Robin Hood and Allan-a-Dale is a traditional English ballad, catalogued as Child Ballad No. 138 and as Roud Folk Song Index No. 3298.
"The Knight and the Shepherd’s Daughter" is an English ballad, collected by Francis James Child as Child Ballad 110.
Now is an album by The Dubliners released in 1975.
 Following the departure of both Ciarán Bourke and Ronnie Drew in 1974, singer/guitarist Jim McCann joined Barney McKenna, Luke Kelly and John Sheahan as a member of The Dubliners to record this album, which Sheahan himself produced.
 The slight shift in personnel produced a more mellow sound.
 Arguably, McCann's greatest contribution to the album is the ballad "Carrickfergus", which became one of his most popular and requested songs.
 It also features a wonderful rendition of the English ballad, "The Unquiet Grave", performed by Luke Kelly.
The Beggar-Laddie is a traditional English ballad existing in several variants.
 It was collected by Francis James Child as Child ballad 280.
"King Arthur and King Cornwall" is an English ballad surviving in fragmentary form in the 17th-century Percy Folio manuscript.
 An Arthurian story, it was collected by Francis James Child as Child Ballad 30.
 Unlike other Child Ballads, but like the Arthurian "The Boy and the Mantle" and "The Marriage of Sir Gawain", it is not a folk ballad but a professional minstrel's song.
 It is notable for containing the Green Knight, a character known from the medieval poems "The Greene Knight" and the more famous "Sir Gawain and the Green Knight"; he appears as "Bredbeddle", the character's name in "The Greene Knight".
"The Unquiet Grave" is an English folk song in which a young man mourns his dead love too hard and prevents her from obtaining peace.
 It is thought to date from 1400 and was collected in 1868 by Francis James Child, as Child Ballad number 78.
 One of the more common tunes used for the ballad is the same as that used for the English ballad "Dives and Lazarus" and the Irish pub favorite "Star of the County Down".
"The World Turned Upside Down" is an English ballad.
 It was first published on a broadside in the middle of the 1640s as a protest against the policies of Parliament relating to the celebration of Christmas.
 Parliament believed the holiday should be a solemn occasion, and outlawed traditional English Christmas celebrations.
 There are several versions of the lyrics.
 It is sung to the tune of another ballad, ""When the king enjoys his own again"".
'Rock-a-bye Baby' is a nursery rhyme and lullaby.
 The melody is a variant of the English satirical ballad Lillibullero .
 It has a Roud Folk Song Index number of 2768.
Effie Crockett (1857 - January 7, 1940), also known as Effie I. Canning, also known as Effie C. Carlton, was an American actress.
 She is credited with having written and composed the lullaby "Rock-a-bye Baby"; by some accounts she created the song in 1872 while babysitting.
 Because of "Rock-a-bye Baby", she is credited in over 100 films, many made decades after her death.
"No Man's Land" (also known as "The Green Fields of France" or "Willie McBride") is a song written in 1976 by Scottish Australian folk singer-songwriter Eric Bogle, reflecting on the grave of a young man who died in World War I.
 Its chorus refers to two famous pieces of military music, "The Last Post" and "The Flowers of the Forest".
 Its melody, its refrain ("did they beat the drum slowly, did they play the fife lowly"), and elements of its subject matter (a young man cut down in his prime) are similar to those of "Streets of Laredo", a North American cowboy ballad whose origins can be traced back to an 18th-century English ballad called "The Unfortunate Rake" and the Irish Ballad "Lock Hospital".
 In 2009 Eric told an audience in Weymouth that he'd read about a girl who had been presented with a copy of the song by then prime minister Tony Blair, who called it "his favourite anti-war poem".
 According to Eric, the framed copy of the poem was credited to him, but stated that he had been killed in World War I.