I chose 'quench' as a medium difficulty word because:
1. It's 6 letters long, fitting within the requirements
2. It's a real English word that uses only standard letters
3. It has an uncommon letter 'q' at the start, making it interesting
4. It has common letters like 'n' and 'e' to give the player some success
5. The 'ch' combination adds a nice challenge
6. It's not an obscure word - people know its meaning (to satisfy thirst), but it's not used in everyday conversation as frequently as simple words