Why do most non-Christian Chinese S'poreans give themselves adopted Western first names?

[True Believer]

My best non Chinese names for Chinese are….they are all real names of my Hongkee colleagues when I was in a bank.
1) Hymen Lam
2) Fanny Pong

The name Fanny is pretty widely adopted in Hong Kong and S'pore by Chinese girls. In the USA and Canada, it is an informal term for buttocks. However, in the UK, Australia and New Zealand, it is actually a vulgar slang term for the female genitalia.