From the Greek for "inquirer", it's someone who doubts the claims of philosophical knowledge
Classical philosophical skepticism derives from the classical Greek verb, .... 
accrues from its role as a foil contrastively illuminating what is required for 
knowledge and... [DOC] [TLE] Skepticism, History of - Dictionary definition of Skepticism, History of ... [PAR] The original Greek meaning of skeptikos was "an inquirer," someone who was 
unsatisfied ... As ancient philosophy and science developed, doubts arose about 
basic ...