Crackaloo

Part of speech: noun

Definitions

1. Someone regarded as mad, eccentric, or foolish, used as an informal and rather old-fashioned term of mild insult
2. An informal, dated slang word for a person who acts crazy or whose behavior seems odd and unbalanced
3. A colloquial label for an eccentric or unhinged individual, often said with light teasing rather than real hostility

Etymology: "Crackaloo" appears to be an echoic formation built on "crack," the sharp, snapping sound, with the rhythmic ending "-aloo" that English speakers have long used in playful or nonsense-sounding coinages. Those details would need a dated citation to pin down.