An invented or obsolete term possibly meant to convey a sense of sharpness, bitterness, or sorrow (from 'egre').
Hypothetical formation from 'egre' plus the suffix -itude (from Latin -itudo), creating an abstract noun; likely never widely used.
This looks like it *should* be a word (following the pattern of 'altitude,' 'gratitude,' 'certitude'), but if it ever existed in English, it's completely disappeared—showing how language deaths happen quietly with forgotten abstract nouns.
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