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mid-15c., present participle adjective from kill (v.). Meaning "very funny" is from 1844. As a noun, "large profit," 1886, American English slang.
Excellent; fresh, great, killer, way rad: And good things are known as ''rad, tough, booming, legit, fly, kill, killing, chilling, fresh or nasty''
make a killing
[1980s+ Teenagers; the sense ''fascinating, bewitching, irresistible'' is found by 1619, but the current use is an independent phenomenon rather than a survival]