Meaning of the Sanskrit Word: trastah

  trastaḥ—frightened    SB 7.9.16
  trastāḥ—frightened    SB 3.17.12
  trastāḥ—frightened of    SB 3.17.22
  trastāḥ—fearful    SB 3.19.17
  trastāḥ—being afraid    SB 4.14.3

Can't find any compound Sanskrit words containing trastah.