намол

Probably from на- (na-) +‎ мол (mol, “cavity”). Bulgarian Etymological Dictionary tentatively also compares Serbo-Croatian му̑љ (“silt”), Ukrainian мул (mul, “mud”), Polish muł (“silt”), however, notes that the vocalism of these forms does not match the vocalism of the Bulgarian lemma.

намо́л • (namól) m (dialectal)

1. deposit of silt, sludge, mud

   В ямата се е насъбрал намол.

   V jamata se e nasǎbral namol.

   A deposit of sludge has filled in the ditch.

2. (by extension) clay soil (low-quality soil with muddy texture)

• подмо́л (podmól, “underground cavity”)

• Georgiev, Vladimir I., Duridanov, I. V., editors (1995), “намол”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volume 4 (мѝнго² – па̀дам), Sofia: Prof. Marin Drinov Pubg. House, →ISBN, page 486