The modern informal adjective 'wiggy' is a relatively recent formation, emerging in mid-20th century American slang. Its primary meaning of "crazy" or "eccentric" derives from the earlier phrase "flip one's wig," a vivid metaphor for losing mental control, as if one's hairpiece were literally thrown off by the force of excitement or insanity. The secondary, positive sense of "excellent" follows a common pattern in slang where terms for extreme states (like "crazy," "sick," or "mad") are semantically inverted to express admiration. Thus, the journey from a concrete noun for a hairpiece to an abstract adjective describing a state of mind showcases the creative and metaphorical nature of colloquial language evolution.

The word is a simplex form. It is derived from the noun 'wig', a shortening of 'periwig', which entered English in the 17th century from the French 'perruque', ultimately of uncertain origin, possibly from Italian 'parrucca'. The '-y' suffix is a productive English adjectival suffix of Germanic origin (Old English '-ig'), used to form adjectives meaning "characterized by" or "full of."