Ginchy morphed into boss, morphed into groovy, morphed into bad, rad, cool, bitchin', sick, etc. etc. (there are likely another hundred words). As Kookie said, "Baby, you're the ginchiest" the best.
1.(n.)A good ole boy, mainly southern, who knows what to say and what to do on every subject. One who loves drinking Captain Morgan. One who likes dancing with dogs and cooking noodles.