The 3 keys words are a triplet, which means that they are linked by a common word. This common word is the Final Word you are looking for to complete the map and finish the quest. This common word can appear after each of the 3 words to form 3 well-known phrases, like this:
___          ____
key #1     final word

________      ____
key #2              final word

_________     ____
key #3                final word