The words ANGERED and DESCANTS can be changed into new words by adding and/or inserting the same three-letter word. What's the word and what are the two new words?

(BIG) HINT:
The same things applies to the word LEG.

Answer:

The word END can be added at the front of ANGERED to get ENDANGERED, and inserted into DESCANTS to get DESCENDANTS. 

(Hint: LEG - LEGEND)

Credit:
Paula Gamache