Why is the dollar called a dollar?

Answer 1

The word "dollar" has a long history dating back to central Europe in the 15th century.

Some of the first large-size silver coins were minted from metal mined in what is now the southeastern part of Germany. Most of the silver veins were found in valleys. The word for valley in old-style German was "Thal", pronounced roughly "tohl". The coins soon became known as Thalers ("tohllers") meaning "from the valley".

Thalers proved to be so popular that similar coins were eventually used all over Europe as a common exchange medium. Each region adapted the name to its local language and spelling; by the time the coins were used in the Netherlands they had become "dalers", still pronounced with a short 'a'. But to those of us accustomed to English spelling that looked too much like it should be pronounced "dayler" so the spelling gradually morphed to something closer to its pronunciation, giving the familiar word DOLLAR.

Why dollars in the US?

When the US adopted its decimal currency a Spanish version of the Thaler called a "real" (ray-AL) was already circulating due to the proximity of Spanish colonies. The Mint decided that the primary American silver coin would be compatible in size and weight with the Spanish coin. Reales were already called dollars in common use so the new American coins were given the same name, but this time it was official.