Meaning

noun a set of rules or principles or laws (especially written ones)

noun a coding system used for transmitting messages requiring brevity or secrecy

noun (computer science) the symbolic arrangement of data or instructions in a computer program or the set of such instructions

originFrom Middle English code (“system of law”), from Old French code (“system of law”), from Latin cōdex, later form of caudex (“the stock or stem of a tree, a board or tablet of wood smeared over with wax, on which the ancients originally wrote; hence, a book, a writing.”). Doublet of codex. Verb etymology 1, verb sense 7 is an ellipsis of code blue (“medical emergency”).

Etymology from Wiktionary, CC BY-SA 3.0