古俗 is read as こぞく (kozoku) and means old custom.
こぞく
kozoku
こてん
classic (work, esp. book)
ふるくさい
stale
こてんてき
classical
こふん
ancient burial mound
ふるす
old haunts
ふるきず
old wound
こごう
veteran
ふるびおとろえる
to waste away
こせいたいがく
paleoecology
こしょてん
exhibition of rare (old, antiquarian) books
ここんどっぽ
unmatched in history
こてんてきじゆうしゅぎ
classical liberalism