Why MAAT and not AT?

I was wondering if anyone on the forums knows why AAT use the designatory letters MAAT rather than AT? as this would be in line with other UK accounting bodies using the qualification rather than the association/institute as the des. letters.

(i.e CA rather than MICAS for ICAS chartered accountants)

(an example is that the Institute of Chartered Accountants in New Zealand (now CAANZ) use AT as the desg. letters for their accounting technicians)