The Etymology of Lingo
Lingo is recorded from the 1660s and was sailor slang from the start. Its likeliest source is Portuguese lingoa (modern língua), language, brought aboard by Iberian seamen working English-flagged ships and through the lingua franca of Mediterranean and Atlantic ports — the pidgin trading speech that itself is named for Latin lingua, tongue. English sailors picked up enough of every harbour to know the word for tongue in many of them, and lingo became a generic, slightly scornful label for any foreign speech they could not follow. From sailors’ usage the word spread inland, generalising to mean specialised jargon — legal lingo, sporting lingo, medical lingo. Lingua franca itself is Italian for "Frankish tongue", the trading pidgin once spoken across the Mediterranean. Lingua, language, lingual, linguine (little tongues, the pasta), and lingo all hang from the same Latin root.