νυσταλός

From LSJ

κέρκος τῇ ἀλώπεκι μαρτυρεῖ → you can tell a fox by its tail, small traits give the clue to the character of a person

Source

Russian (Dvoretsky)

νυστᾰλός: v. l. νύστᾰλος 2 сонливый, сонный Diog. L.