Meaning of the Sanskrit Word: tamasam

  tāmasam—in the mode of ignorance    Bg 17.13, Bg 18.25, Bg 18.39
  tāmasam—in the mode of darkness    Bg 17.19, Bg 17.22, Bg 18.22
  tāmasam—material elements    SB 5.17.22-23

Can't find any compound Sanskrit words containing tamasam.