Answer:
Idiom.
Step-by-step explanation:
A lingo refers to a language that is specific in it's meaning and peculiar to a particular group of people, region, association or field.
An idiom can be defined as a literary technique or device that is used in everyday language but it's not meant to be interpreted literally.
Basically, idioms are phrases that may be impossible to interpret or difficult to understand based on a loose translation of the words contained therein. Therefore, idioms shouldn't be interpreted literally but in a figurative sense.
Some examples of common idioms and there meaning include the following;
I. Make a hay while the sun shine.
II. A picture is worth a thousand words.
Hence, if you didn't understand the lingo used in a book, you don't understand an idiom.