How did Cardiff come to be called Cardiff,seeing as its Welsh name is completely different?

and what does the name Cardiff mean?

How did Cardiff come to be called Cardiff,seeing as its Welsh name is completely different?
Caerdyf, a form which dates to the early 6th century at least, contains two place-name elements. The first is Welsh caer, 'fort, stronghold, enclosure' which is often seen in Welsh place names. This is followed by Taf, a river-name in its genitive form Tyf, mutated to Dyf - 'fort (of the river) Taf'.





The form Cardiff recorded in 1477 represents an anglicised pronunciation of Caerdyf, while Caerdydd demonstrates the interplay between the f and dd consonants in the Welsh language.
Reply:The very first Ford car that was imported into Britain was running through wales many years ago,when it suddenly broke down,there was a nearby garage,and they told the driver what the trouble was and how much,but he was deaf and shouted EH?'? The mechanic screamed in his ear --"ITS THE CAR DIFF" and the area has been called that ever since.
Reply:The welsh pronounciation for Cardiff is Caerdydd. which traslates in English to Day fort or Castle. Historians however believe it should be Caertaft. This would translate to the castle by the taff. The Norman castle in Cardiff is on the banks of the river Taff, so this would be more acceptable as an explanation of The name Cardiff.Any town in Wales that has the word Caer in the name , means there is a Castle there such as , Caerphilly, Caernarfon etc.
Reply:In Welsh the name is Caerdydd. The original meaning is unclear: it's the name of a fort or castle. Cardiff is a spelling of an English attempt to pronounce Caerdydd.
Reply:Cardiff in welsh appears as Caerdydd. It seems that a Roman called Didius, while serving as governor of Britain, had a fort built and it was named after him. Later after the Romans had left the local Britons still called it the fort of Didius, or Caer Didi in their language. Later the name evolved into Caer Dydd.


The fort was built next to the river Taff, and there are some who think the name of the river and the name of the Roman have been confused and ended up being blended together to get the ff ending in english.


It is also possible that the welsh accent made the dd (pronounced like th in the word breathe) of dydd sound more like an f sound.