User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-28209103-20170328065900/@comment-28209103-20170328093511

Chaldea are actually special way to refer to Casdim.. and Casdim are famous for?

There's no implified meaning here... however as you've guessed it's some unusual choice of word. However it is not unfair as the FGO main story already covered the meaning albeit imperfectly.

Here's a hint, it's Rani speciality