1. What do the following words have in common?

BEEP
POOH
EXTRA
EXCUSES

2. What do the following words have in common?

LOT
LEG
SECT
FACT
PORT

Answers:

1. They are commonly repeated twice. 

2. Each word can be followed by ION to make a new word:

LOTION
LEGION
SECTION
FACTION
PORTION