I've known "the Bitter Withy" for years, in Peter Bellamy's version, when he was with Young Tradition. I've always thought the first two lines were:
"As it fell out on a bright holiday,
Small ale from the sky did fall".

Isn't this just a figurative term - everywhere you look there's small ale (i.e. weak beer) - like the modern "it's raining men"!

If it was a bright holiday and the infant Jesus built a bridge from the beams of the sun, how come it was hailing? And why "small" hail?

I rest my case.