Photo: Wikimedia Commons
The two oldest known names of the city are Kakamuchee and Galajunkja. Though some people still identify these names with the city, it was not in popular usage.
But during the European invasion, Portuguese people called the city as ‘Bombaim’, which means ‘good bay’. When the British shifted East India Company headquarters to Mumbai from Surat to the city in the 17th century, they anglicised ‘Bombaim’ to ‘Bombay’.
Then how it became Mumbai again?
When Shiv Sena came into power in Maharashtra in 1995, they wanted to shed the legacy of British colonialism. The party wanted the city’s name to reflect the Maratha heritage. Thus officially, Bombay became Mumbai – named after the goddess Mumbadevi, the city’s patron deity. In November 1195, the central government officially changed the English name to Mumbai in November 1995.
Source: https://news.google.com/__i/rss/rd/articles/CBMigAFodHRwczovL3d3dy50aW1lc25vd25ld3MuY29tL211bWJhaS9ib21iYXktdG8tbXVtYmFpLXdoeS1kaWQtdGhlLWNpdHktY2hhbmdlLWl0cy1uYW1lLWFuZC13aGF0LXdlcmUtdGhlLXJlYXNvbnMtYXJ0aWNsZS05NTMxNTkwN9IBAA?oc=5