Pound must've been outrightly impressed by the Old Possum's evasive tactics in 'Prufrock': 

To lead you to an overwhelming question….        
Oh, do not ask, “What is it?”  

And would it have been worth it, after all,
Would it have been worth while,        
After the sunsets and the dooryards and the sprinkled streets,
After the novels, after the teacups, after the skirts that trail along the floor—
And this, and so much more?—
It is impossible to say just what I mean!

Till human voices wake us, and we drown.


On Sunday, October 11, 2015, Chanan Mittal <[log in to unmask]> wrote:
From Rick's find:

The nicknames were no mistake — Pound viewed himself as a brash risk-taker, while he considered Eliot’s reserve to be quietly subversive. True to form, Eliot even signed one of his letters “Tar Baby” (as in the story where the “Tar-Baby ain’t sayin’ nothin'”).


Pound, I guess, would liken Tom to a possum for he (Tom) partook of that animal's behavioral trait of feigning ignorance, sleep or death as a defensive tactic. 


On Sunday, October 11, 2015, Rickard A. Parker <[log in to unmask]');" target="_blank">[log in to unmask]> wrote:
On Sun, 11 Oct 2015 02:12:21 -0700, P <[log in to unmask]> wrote:

> So CR,  any idea why Pound nicknamed Eliot Ol' Possum?

I took 60% of this query (why Pound nicknamed Eliot Ol' Possum) and stuck it into Google. The first hit explained it:

The second hit was scholarly:
   The Dialect of Modernism: Race, Language, and Twentieth-century Literature
   By Michael North
   Old Possum and Brer Rabbit: Pound and Eliot's Racial Masquerade

   Rick Parker