'forefend' is a correct and usable word in written English. It means "to prevent or ward off", and can be used in contexts when you want to express the idea of being proactively careful or taking measures to avoid something. For example: "We must take precautionary measures to forefend a worse outcome".
On his Web site Tuesday, he urgently vowed to establish a White House commission "On Day One" of his presidency (heaven forefend) "to examine and document threats or impediments to religious freedom in the United States".
We like to argue about them, too - it's a quintessentially British way of bonding without revealing too much emotion (heaven forefend).
You doubtless don't want to blunder into someone's precious tea party (heaven forefend), but you are a Leo and currently licensed to thrill.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union