Green’s Dictionary of Slang

funk n.2

[orig. Oxford Univ. use; ult. Flemish fonck, fear]

1. [18C+] (a state of) cowardice, terror.

2. [late 18C+] a black mood; a state of depression; thus funking adj., furious.

3. [mid-19C+] a coward.

4. [1900s] (Aus./US Und.) an informer.

5. [1920s–30s] (US tramp) a sneak thief.

6. see Peter Funk n. (1)

In compounds

funkhole (n.) (also funkpit)

[1910s+] (orig. milit.) anywhere one can hide.

In phrases

on the funk (adj.)

[early 19C] in a bad mood.