From Wiktionary, the free dictionary
From 過去 (kako, “past”) and 一番 (ichiban).
かこいち • (kako-ichi)
- (slang) most … up to this point in time
- 過去一かっこいい
- kako-ichi kakkoii
- the coolest I've ever seen
かこいち • (kako-ichi)
- (slang) of the greatest levels up to this point in time
- 過去一のかっこよさ
- kako-ichi no kakkoyosa
- (please add an English translation of this example)