This phrase has entered the
lexicon from the classic story of the
Three Little Pigs:
Wolf: "Little pig, little pig, let me in!"
Pig: "Not by the hair of my chinny chin chin!"
"The hair of my chin" is the
beard, for a long time
an important symbol of
maleness in Christianity,
and still one in (eg.)
Islam and
Sikhism. The phrase
"
by my beard" was a mild oath used by
Shakespeare
among others (cf.
The Two Gentlemen of Verona, Act 4,
Scene 1), implying that the speaker would rather
emasculate his chin than fail to live up to his promise. Here "hair of my chin" is used because it rhymes with "in", and padded with three extra syllables to make it fit the meter.
The odd part is that pigs do not have much in the way
of a beard, but perhaps that only serves to make the
rhyme more memorable. Another possibility is that the
pig was speaking Japanese, in which case the phrase
takes on a rather different meaning...
A nodeshell rescue! w00t!