means A large molecule made of chains of amino acids that does most of the actual work in your cells — building tissue, speeding reactions, carrying signals — and a vital part of your diet.

from Coined in the 1830s, when chemists realized these substances were fundamental to all life. The name traces to Greek 'proteios,' meaning 'primary' or 'of first rank,' itself from 'protos,' 'first' — the same 'first' you hear in 'prototype' and 'protagonist.' The naming is often credited to the chemist Berzelius, who suggested it to a colleague precisely because these compounds seemed to come first, the foundation everything else was built on.