Not by the hair of my chinny chin chin!

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!

Allow me to elaborate on gn0sis's writeup above.

Never.

NEVER.

Never use this phrase in Japan. In fact, skip The Three Little Pigs altogether, everywhere in Asia, just to be on the safe side.

This is doubly true if you're teaching English to a group of Japanese 8-year-olds. I'll cut to the chase here. You see, in Japanese, the word "chinchin", or "chinko", is baby-talk for "penis", along the lines of "dick", "willie", "dinkie", or, as gn0sis suggests, "weewee".

Many Japanese people already know the word "hair" as it exists in many product names. So, as the pigs defiantly (and, invariably, nakedly) taunt the wolf, the kids will hear this:

garbagegarbagegarbageHAIRgarbagegarbagePEENIE PENIS.

In fact, this is probably what any Japanese adults who are supervising you will hear as well. If you live in a small town, pretty much everyone will now know you as "that foreign guy who told our kids about pubic hair." Your chances of continued employment as an already suspicious English teacher will be even slimmer than before.