Comparative form: more fretty; increasingly worried, nervous, or displaying more fret patterns.
From 'fretty' (adjective) + the comparative suffix '-er', following standard English pattern for forming comparative adjectives from base adjectives.
Frettier is such a niche word that most English speakers would just say 'more fretty' instead—it shows how English grammar allows formations that don't always get used in practice.
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