treacle

Treacle comes from Middle English triacle, arriving partly through Old French triacle and partly through Old English tyriaca, both tracing to Late Latin *triaca/*tiriaca, a late form of theriaca. That word goes back to Ancient Greek θηριακή (thēriakḗ), meaning 'antidote,' the feminine form of θηριακός, 'concerning venomous beasts,' from θήρ (thḗr), 'beast.'

Treacle is a doublet of theriac, both descending from the same Late Latin *triaca/*tiriaca root, just shaped by different paths into English.