That s a misunderstanding by those unfamiliar with asian culture there is a vietnamese dude I know who does the same thing In your wife s case Sin Ho is the formal form of her first name either the first or the second character can be used as a pet name by the family so those unfamiliar with their culture take it as a main first name The family may also use some variations of this as a petname like Sin Sin Ah Sin Siu Sin or otherwise Ah Ho etc there are asians who consciously decide to use it as their main name kinda akin to someone named William tells you to call them Bill but in most circumstances if you don t know that person well it s considered disrespectful