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

1. MOUNTAIN

2. SURGERY

3. CURTAIN

4. NICKELS

5. NERVES

6. TIGER

7. OVEN 

Answer:

 

Each word can be preceded by a kind of material to make a familiar name or phrase:

 

1. STONE MOUNTAIN

2. PLASTIC SURGERY

3. IRON CURTAIN

4. WOODEN NICKELS

5. STEEL NERVES

6. PAPER TIGER

7. BRICK OVEN