Literal meaning:
The speaker is no one, it would be horrible to be someone. Someone public is a frog in a bog
"I am nobody!"(line 1)
"How public- like a frog" (line 6)

Figurative meaning:
The speaker doesn't want to be publicly known and finds the thought of being out in the open to be dreadful
"How dreadful- to be- somebody!/ How public..." (Line 1,2)

Topics:
The taste for being in the public eye
"Don't tell! They'd advertise- you know!" (Line 4)

Topic: