What do the following three-letter words have in common that has nothing to do with their meanings?

1. BAN
2. TOT
3. LEG
4. FIN
5. TUB

HINT:
The same two letters will change each word into a new one.

Answer:

The letters AL can be added to the ends of the clue words to make new words:

1. BANAL
2. TOTAL
3. LEGAL
4. FINAL
5. TUBAL