An Acronym is a word that is formed with the initial letters of the word.But I came across something called a Backronym. A word is said to be a backronym if it started as an acronym and later got an expanded version! Well,an example would make it more clear -SOS was a backronym. But it later came to be known as 'Save Our Souls' / 'Save Our Ship'.
The word Backronym is a Portmanteau!The word Portmanteau was coined by Lewis Caroll. To define a portmanteau, it is a word that is formed by combining the sounds and the meanings of different words. Ha, would you believe if were to tell you that TomKat actually stood for Tom Cruise and Katie Holmes? (Spare me geeks!Please.....)
If a word is either an acronym/a backronym and also has a meaning related to the words it is made up of,is called an Apronym. Apronym is a portmanteau of Appropriate Acronym! A famous example is - Lucy in the Sky with Diamonds, for LSD.Well, this falls under the acronym category.The one in the backronym category is - INFINITY, wherein it stands for Increment Numbers Forever -It's Nuts, I tell You!