Final answer:
The small openings in the lid of a closed-head drum are called bungs and are used for accessing the drum's content.
Step-by-step explanation:
The small openings in the lid of a closed-head drum are known as bungs. These openings serve as access points to fill or release contents without opening the entire drum lid and are typically plugged with a bung cap to prevent spillage or contamination. The term 'bung' accurately describes these features in containers used for transporting liquids or other substances that require a secure seal.