1
general::
Phrase(s): push someone or something off (of) someone or something [and] push someone or something off
to apply pressure to and force someone or something off someone or something. (Of is usually retained before pronouns.) • He continued to come at me, but I managed to push him off me and escape. • I pushed off the attacker., Phrase(s): push (oneself) off (on something)
[for someone in a boat] to apply pressure to something on the shore, thus propelling the boat and oneself away. • The weekend sailor pushed himself off on the boat he had been moored to. • We pushed off on the dock., Phrase(s): push off [and] shove off
to leave. (As if one were pushing a boat away from a dock.) • Well, it looks like it’s time to push off. • It’s time to go. Let’s shove off.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, shove off. Leave, set out, depart, as in The patrol pushed off before dawn, or It's time to shove off. This usage alludes to the literal meaning of a person in a boat pushing against the bank or dock to move away from the shore. [Colloquial; early 1900s]
American Heritage Idioms