[CentOS] What is cached swap?

Isn't cached swap somewhat an oxymoron? Why cache virtual?
Am I misunderstanding this line from top?

Swap:   524120k total,    80760k used,   443360k free,    73448k cached

Mike
-- 
p="p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}
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