JTT - Gargoyle has it right, it starts at one & goes up to the 12 - adding one each time to the list.

It seems 'right' to me that only the lowest two have a couplet, when you get down to the 3-2-1 bit its more elaborate because you've arrived (well it makes sense to me). In the same way, the lowest few numbers of 12 days of christmas are more elaborate. If you imagine an informal bunch of people singing these songs they will tend to take more effort to remember the higher numbers (because less repetition=less sure memory) & will then sing the lower few with great gusto & relief at having got there. Imagine having to remember 12 couplets!!!!!!! I'd never get through it.

The two lilly-white boys seem a bit pagan to me - dressed in green & all.

Kris