The Hearse Song

"The Hearse Song" is a song about burial and human decomposition, of unknown origin. It was popular as a World War I song, and was popular in the 20th century as an American and British children's song, continuing to the present. It has many variant titles, lyrics, and melodies, but generally features the line "the worms crawl in, the worms crawl out", and thus is also known as "The Worms Crawl In".
History.
The earliest version of the verse is found in a poem by the English writer Matthew Lewis, incorporated in his popular 1796 Gothic novel "The Monk", which includes the lines "The worms they crept in, and the worms they crept out and sported his eyes and his temples about." While there are reports of the song dating back to British soldiers in the Crimean War (1853–1856), it certainly dates to at least World War I (1914–1918), when it was sung by American and British soldiers, and was collected in various World War I songbooks of the 1920s. The key line "the worms crawl in, the worms crawl out" appears in some versions of the otherwise unrelated song "There was a lady all skin and bone", and may date to 1810 or earlier.