Green’s Dictionary of Slang

chickenshit n.

[chicken n. (2a)/SE chicken + shit n. (1a); the cowardice of the person/the essential insignificance of the substance]
[1930s+] (orig. US)

1. something insignificant, worthless.

2. (also chickenstuff) a coward.

3. a contemptible, disgusting person.

4. a disgusting, unacceptable action or situation.

5. (US milit., also chicken) meaningless, petty discipline.