How did Calcium get its symbol Ca?

Answer 1

Calcium gets it's symbol "Ca" from the first two letters of its name.

Like all elements, it's symbol is derived from its name, although not necessarily it's English name (such as in the case of sodium {Na}, or tungsten {W} to name a few examples).

Luckily, in the case of calcium, "Ca" are the first two letters in both it's English name and it's Latin name (calx).

Answer 2

The symbol Ca for calcium comes from its Latin name "calcis", meaning lime or chalk. It was derived from the Latin word "calx", which referred to limestone.