IPA: /ˈmɛdɪkəmənt/
KK: /mɛdɪkəmənt/
A substance that is used to treat or prevent illness or to promote healing.
The doctor prescribed a medicament to help with her recovery.
Medicament is formed from "medicari" (meaning to heal) and the suffix "-ment" (indicating the result of an action). The word refers to a substance that produces healing or therapeutic effects.
Think of 'healing' ('medicari') and the result of that action ('-ment') — that's why medicament means a healing substance.