Може от содата за готвене да са взели името в разговорната реч.
Не зная.
Поне името знаех, но откъде идва и защо е разликата, нямам представа.
Питах ИИ-то.

Why they call it sodium when in the periodic table of elements it is Na?
The element is called sodium in English (and in many other languages), but its chemical symbol on the periodic table is Na because the symbol comes from its Latin name: natrium.
Here's the quick backstory:
The word "sodium" was coined in 1807 by English chemist Humphry Davy when he first isolated the pure element (by electrolyzing sodium hydroxide / caustic soda). He based the name on "soda," referring to soda ash (sodium carbonate), a compound long known and used for centuries.
However, before the element itself was isolated, people already knew various sodium compounds (like natron, a naturally occurring mixture of sodium salts used in ancient times for mummification, soap, glassmaking, etc.).
Those compounds were called natron in many European languages — a word that traces back through Arabic (natrun) to even older origins.
In the early 19th century, when the system of chemical symbols was being standardized (especially by Jöns Jacob Berzelius), the Latinized name natrium was adopted for the element in scientific Latin (the international scientific language at the time). The symbol was therefore taken from the first two letters: Na.