Plural of foulness; multiple instances or aspects of the condition of being foul.
From 'foulness' + the plural suffix '-es.' This plural form is rarely used because 'foulness' is typically a mass noun (uncountable), but it can be pluralized when referring to different types or examples of foul things.
It's rare to use 'foulnesses' because we usually treat foulness as uncountable (like 'dirt' rather than 'dirks'), but medieval writers did occasionally pluralize it to mean different kinds of wickedness or different foul smells—showing how word countability shifts over time.
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