大方廣圓覺修多羅了義經略疏 1.792

1.792

六根、六塵是生識處。處是生門義故，亦名為人。意識常昏，根塵相入故。

The six faculties and six dusts are the places where consciousness arises. Because 'base' (āyatana) has the meaning of a gateway of arising, it is also called 'doors.' Because the mental consciousness is constantly confused, the faculties and dusts enter into one another.