Simplify the following text for a Grade 11 native English-speaking person.
Original: The city was officially referred to as Trivandrum in English until 1991 , when the government decided to reinstate the city 's original name Thiruvananthapuram in all languages .
Simplified: The city was officially known as Trivandrum in English until 1991 , when the government decided to change the city 's name back to the original name , Thiruvananthapuram , in all languages .