UTM is Urchin Tracking Module

UTM is something you may come across first in URLs. 

UTM refers to Urchin Tracking Module, named after Urchin, the firm Google acquired in 2005 to form the basis for Google Analytics.

• utm_source denotes a tracking parameter in a URL - to denote where traffic is coming from
• utm_source=google indicates traffic came from google
• utm_source=email traffic came from an email

Google Analytics alternatives such as Plausible have been built which follow the UTM convention.

What is Snake Case in Computer Programming?

Snake case is a way of writing compound words, so that each word is separated by an underscore symbol. An example would be "cavendish_laboratory" or "sainsbury_laboratory". 

It is meant to be easier to read than camelCase, _camelCase or PascalCase.

A variant, Kebab Case, uses dashes and though commonly found in URLs, is also used in other contexts e.g. SPARQL-QUERY.