Why on earth Maltworms?

I first came across the word Maltworms in a drinking song written by the composer Moeran, who was a bit of a boozer himself — apparently it comes from the 16th century and its early modern origins reminded me of the joy with which I had savoured similar drink-orientated words of the time, such as pot-valiant, a word that I seem to recall being used in Shakespear, probably referring to the likes of Falstaff, whose martial boasts would depend on the amount of sauce he had put back. According to various dictionary definitions a maltworm is a tippler and a toper and — presumably — a pot-valiant, which puts Falstaff very much in the frame. These days I’ve not come across it being used to denote a love of malty beers, such as hophead gets chucked about when the IBU queens spring forth. Maybe the idea of someone being called a worm is not the same as being called a hophead, with its references to potheads and crackheads (a denuded belief that an excess of narcotics opens up the doors of perception and other such dopey things). At least we haven’t got yeast beasts…
Onto the words of the song. I do love the first verse, which suggests someone with a delicate constitution who, fair play, is not ill enough to give up the ale — ‘I cannot eat but little meat,/ My stomach is not good;/ But sure I think that I can drink/ With him that wears a hood.’ I think we’ve all been there.
*That simple looking maltworm is not me by the way.