Why "Pig" in "Pig Latin"?

[Gerald Cohen]

   Would anyone know why "Pig" appears in "Pig Latin"?  Might it have
derived from children insulting each other with the word "pig" in a
disguised form?  OED is silent on why "Pig" appears in "Pig Latin",
but one of its examples contains the pig insult:

1959 I. & P. OPIE Lore & Lang. Schoolch. xiv. 321 'Pig Latin'..thus:
'Unejay ithsmay isay igpay' (June Smith is a pig).

    This 1959 example comes well after the start of Pig Latin (first
attestation: 1937; but assumed to have started prior to World War I).
Still, maybe this sort of pig-example was spoken early on in Pig
Latin.

Gerald Cohen