虎の威を借る狐
(Tora no i wo karu kitsune; “a fox borrowing a tiger’s menace”)

Definition:

A person without much personal authority, power, or menace, such as a child or servant, acting high and mighty due to their association with someone who has real power. Borrowing the influence of others.

Breakdown:

This noun phrase comprises two nouns – an object and a subject – and a verb. The primary noun is 狐 (kitsune), “fox.” It’s modified by the verb 借る (karu), “to borrow,” in prenominal form. The thing being borrowed is 威 (i), “dignity” or “menace.” This noun is marked by the associative particle の (no) as belonging to 虎 (tora), “tiger.”

Notes:

借る (often 借りる, kariru, in modern Japanese) may be written as 藉る – a rare character that in this usage yields identical pronunciation and meaning.

This saying comes from the Chu section of a historical text known as the Strategies of the Warring States, from (when else?) the Warring States period of Chinese history. The text contains a fable about a fox caught by a tiger who convinces the tiger to follow behind him and see how terrified the other animals are of the fox… the other animals flee from the tiger, who is nevertheless tricked into believing that the fox has divine backing and should not be eaten.

Example sentence:

「柔道部のキャプテンの弟が低学年の子たちをいじめてるらしい。まったく、あの虎の威を借る狐！」

(“Juudoubu no kyaputen no otouto ga teigakunen no kotachi wo ijimeteru rashii. Mattaku, ano tora no i wo karu kitsune!”)

[“I hear that the judo club captain’s younger brother is bullying the underclassmen. Seriously, hiding behind his big brother like that!”]