古譚 is read as こたん (kotan) and means old tale.
こたん
kotan
ふるぼん
secondhand book
こてん
classic (work, esp. book)
こだい
ancient times
こきん
ancient and modern times
ふるい
of the distant past
こぶんしょ
pre-Meiji era document addressed to someone in particular
こぶつ
antique
こまい
old rice
こぼく
old tree
こじ
old temple
こじょう
old castle
こふう
old-fashioned