This rhyme is fairly old. It's sort of a riddle rhyme because if you slur it… people have no idea what you're talking about… it sounds like you're speaking in a different language from English. That's the secret behind this rhyme!

Notes

From "Inland printer/American lithographer, Volume 57" (1916):

"Here are a few sentences which, if pronounced in the usual slurring fashion, will puzzle the listener to interpret:

'Mares eat oats;
does eat oats;
little lambs eat ivy;
kids eat ivy too.'

It will sound like

'Marezedotes,
doezedotes
littlelambszedyvy
kidzedyvy too.'"

*****

Here's another version I was sent:

Mareseyt ohts and ghoats eyd ghroats
and liddle lhambs eyd ivy
wouldnt yuo like to eyt ivy too.

Watch
A sung was written around the rhyme, called "Mairzy Doats and Dozy Doats". It was copyrighted in 1943 by Milton Drake, Al Hoffman & Jerry Livingston. Here's a part of it:

Mairzy doats and dozy doats and liddle lamzy divey
A kiddley divey too, wouldn't you?
If the words sound queer and funny to your ear, a little bit jumbled and jivey,
Sing "Mares eat oats and does eat oats and little lambs eat ivy."

Here's a clip of the song...
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