Stephen Fry using the phrase higgledy-piggledy is maybe the most British thing that has ever happened.
According to Dictionary.com, we don't know the origin of the phrase higgledy-piggledy, only that it first appeared in the 1500s. The Phrase Finder website tells us that higgledy-piggledy is a reduplicated phrase - a phrase in which the second word repeats the sound from the first word, one or both words often being nonsense words. Other examples include helter-skelter, jibber-jabber, and hanky-panky. The Phrase Finder also admits that no one knows the origin of the phrase, but points out that a herd of pigs does sort of epitomize the phrase higgledy-piggledy.
Wikipedia tells me that there are actually several types of reduplication in the English language. There's rhyming duplication - like all the examples above. Wikipedia also gives hoity-toity, which I just realized is a double diphthong.
There's also exact reduplication, according to Wikipedia, like bye bye and no-no. Shm-reduplication is a type of rhyming reduplication in which the second word is the same as the first word, but with the first consonant replaced by shm. Fancy-shmancy, cancer-shmancer, etc. This type of reduction comes from Yiddish, and found its way into our mouths by jumping from Yiddish to the New York dialect before going national.
|A gorilla - scientific name: gorilla gorilla. When exact reduplication|
occurs in biology it is called a tautonym.