Comparative form of 'batty'; more crazy, eccentric, or behaving erratically.
From 'bat' (insect) used metaphorically for eccentric behavior, + comparative suffix '-er'. The original 'batty' may reference bats flying erratically.
Calling someone 'batty' stuck around because bats literally fly in chaotic patterns—so 'battier than a cave at dusk' became a way to describe someone acting increasingly unhinged!
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