The Zulāl or Snow-worm is a small worm, the length of a human finger, that breeds in snow. It has yellow spots. The water inside of a zulāl is cold, pure, and refreshing, so it is often captured by humans to drink its contents. The term zulāl is also used to mean cold water on its own, without worms involved. This is now the current use of the term in Arabic and the snow-worm is all but forgotten.
While a zulāl is a worm and unclean, the water inside it is of exceptional pureness and is perfectly safe to drink.
Al-Damiri, K. (1891) Hayat al-hayawan al-kubra. Al-Matba’ah al-Khayriyah, Cairo.
Jayakar, A. S. G. (1908) ad-Damiri’s Hayat al-Hayawan (A Zoological Lexicon). Luzac and Co., London.