IPA: /dɪˈkɒkʃən/
KK: /dɪˈkɑkʃən/
A liquid made by boiling herbs, plants, or other substances in water to extract their flavors or properties.
She prepared a decoction of ginger and honey to soothe her throat.
Decoction is formed from "de-" (meaning down or away) and "coctio" (from "coquere", meaning to cook). The word refers to the process of cooking something down, typically to extract flavors or medicinal properties from herbs or plants by boiling them in water.
Think of 'cooking down' ('coctio') something to extract its essence, which is what decoction means.