It is only a convention.
The original word for potassium in Latin is kalium. That is where you get K for the element , Potassium.
The name of the chemical element hassium is derived from Hassia, the Latin name of the German land Hessen.
Latin
Copper, that wonderful metal we use for electrical wire and piping, was known to ancients. Its use dates back thousands of years. It was called cuprum back in the day, which is Latin. And that Latin name is the source of its chemical symbol, Cu.
They come from Latin words I think.
Most elements symbols come from their latin names. There is more than one element with a name beginning in N so to distinguish nickel from nitrogen (you couldn't write them both as N) one is written as N and the other as Ni
Potassium.
Potassium is kalium in Latin.
Potassium's chemical symbol K comes from the Latin word kalium.
Latin, Greek and proper noun derivatives
You may be familiar with natrium used for sodium in Germanistic languages, chemical symbol Na is the short writing for this element. This element gets its chemical symbol from its Latin name (just as copper does from cuprum, so that became Cu).The Latin word natrium comes from the Arabic word 'natrun'. And the ancients didn't know the element sodium as it wasn't isolated until the 19th century. But they recognized salt, soda, and other sodium compounds.The name sodium comes from the Arabic word 'suda' meaning headache, as soda (sodium (bi)carbonate) was known to be a pre-mediaeval anti-headache medicine.
Visene (there's a Visene for that!) come from the Latin videre, meaning to see