In a foaming state; producing or covered with foam or froth.
From 'a-' (in the state of) + 'foam,' where 'foam' comes from Old English 'fam,' from Proto-Germanic, ultimately related to Latin 'pumex' (pumice).
When King Lear rages on the heath, Shakespeare could describe him as 'afoam at the mouth'—a single word that captured both anger and loss of control in ways modern English requires multiple words to express.
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