We use phrases every day in the English language. If you want to become a colloquial genius, studying these and more importantly, understanding them, is key.
So, to start with...
Holy
(adj): Sacred, divine, blessed.
Holiday: a holy or festive day; a day off, vacation (also sacred)
Expressions: Holy Cow! Literally true in India.
Ex: Holly Mackerel! Delicious, healthy and full of mercury.