The word “lingo” was devised from the Latin word “lingua,” meaning “tongue.” It refers to language that is spoken by a particular section of people that is incomprehensible for anybody outside this specific section.
Often used as an abbreviation for “language,” “lingo” is predominantly used as an identity differentiator. For example, I am unaware of the lingo you speak.
As such, lingo can be of many kinds. You may have Cowboy lingo, used by cowboys on ranches and you may have Hospital lingo, used by doctors and nurses on duty. On the other hand, “white house,” “grub house,” and “dog house” are all words borrowed from Cowboy lingo. Similarly, “banana bag” and “wallet biopsy” are examples of hospital jargon/lingo.
In other words, lingo is any form of speech that differs from the standardized language spoken by mainstream society. It is only used by and understandable for a subset of people. It helps cement shared identity among these people.
Like jargon, it differentiates this group of people from the common public. Lingo is usually passed down culturally and is more resistant to outside influence than languages. Learning a culture’s lingo is a good way to familiarize oneself with that culture intimately.