1. What do the following name and words have in common?

CODE
ARCANE
CONCORDE
COAL MINE

2. What do the following words have in common?

NET
INDEED
ETERNAL

Answers:

1. Each name and word is made up entirely of US state postal abbreviations.

2. Each word can be changed into a new one by inserting the letter X:

NEXT
INDEXED
EXTERNAL

Credit:
#2: NY Times Crossword
      October 13, 1996
      Wayne Robert Williams