Will do a little more later; this does interest me, as it turns up all over MOST religions. I've seen it mentioned many times in documentaries about religions.
The site is a PDF site, requires Acrobat Reader. At the bottom right of the first page it does talk about the number 40 possibly referring to an undetermined length of time. Hope it helps.
705 'arba`iym {ar-baw-eem'} multiple of 702; TWOT - 2106b; n,adj pl AV - forty 132, fortieth 4; 136 1) forty
You might make a case that 40 infers many but it is the literal translation.
What I find interesting is that 40 weeks is the human gestation period.