>>I don't know the etymology of <pylimas>, but it doesn't look as if it
could be derived from *plh1- in any regular fashion.
The etymology is quite clear. Pylimas (rampart) is derived from the word
pilti ("to pour, to strew") (pila - "he pours", pyle. - "he poured";
pylimas - pouring (process; the only difference between pylimas "rampart"
and pylimas "pouring" is accent, which is on "y" (i:) in the first case, and
on "i" in the second case). Thus it is derived from *plh1-, ad very likely
<pilis> is too.