The quality of being somewhat faint; a slight degree of faintness or weakness.
From 'faintish' (adjective) plus the noun suffix '-ness.' This double-suffix construction ('faint' + '-ish' + '-ness') shows English's ability to layer morphemes for precise meaning.
When English speakers layer suffixes like this, they're essentially saying 'the state of being kind of faint'—it's a way of hedging or expressing uncertainty about the degree of a quality, very useful in scientific or precise description.
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