As in ghana घन - ‘thick’, mass
伽字門，入諸法厚不可得故
Kumarajiva
入鍵字門，悟一切法厚平等性不可得故
Xuanzang
Because things and persons are not apprehended each as one solid mass (ghana)
Conze
The syllable GHA [means] all mental phenomena are openings because of the non-recognition of the killer (ghana).
Jayarava