qunnoq
>> Does anyone know, whether the word {pugh} is inherently singular or plural ?

AFAIK {pugh} has never been used in canon but I see it as one of the mass nouns - like {bIQ} “water” and {logh} “space” – which are grammatically singular in Klingon.  {pIgh}, {DI}  and {veQ} seem to work the same way:

pIgh                      ruins (n)

pIraQSIS maS bIngDaq pIgh rur SaqSub chIm choSlu’pu’bogh
The Saq'sub lay empty and desolate under the Praxis moon. PB

ghach jIvvo' naH.  DaH pIghvamDaq So''eghtaH.

There is a criminal hiding in these ruins. STID

DI                          litter, rubble, debris (n)

qatlh Dat DI tu'lu' tlhIngan

Why is there rubble everywhere, Klingon? CK

vaj toDuj Daj ngeHbej DI vI'

Shooting space garbage is no test of a warrior's mettle. ST5/TKW

["Sharpshooting of the cosmos' litter inconclusively tests a warrior's courage."]

veQ                       garbage (n)

logh veQDaq bachchugh, yoH 'e' toblaHbe' SuvwI'

Shooting space garbage is no test of a warrior's mettle. (ST5 notes [original line])

jogh veQ lungIv

They patrol the quadrant garbage. KGT

--Voragh