A 1960s slang word.
The first usage of this word seems to be from the novelty song Kookie, Kookie, lend me you comb (1959), by Edd Kookie Byrnes. He actually used the word "ginchiest" ("Baby, you're the Ginchiest"), not ginchy. The whole 'song' is a bit spaced out, and it would be completely in character for him to make up a new word.
'Ginchy' was interpreted by the youth of the day as meaning that a person or thing was excellent, admirable, and/or elegant.
In 1970 Chip Harrison used the word ginchy to mean nervous or jumpy. I have not heard it used in this sense by anyone else, but the Random House Historical Dictionary of American Slang saw fit to include this definition, so I assume it caught on somewhere, somewhen.
Probably unrelated information:
- There is a town in Ireland called Ginchy.
- The slang word Ginch has been used since the 1930s to mean a sexually attractive or active girl. Ginch is considerably more vulgar than ginchy.