If need (or needs) be?

Q: In the Game of Thrones TV series, Tywin Lannister says to his son, Tyrion, “You’ll bring that boy-king to heel, and his mother too, if needs be.” Why is “if needs be” constructed with the singular verb “needs.” A: The word “need” can be a noun, a verb, or an adverb. It’s a noun meaning a “necessity” or an “obligation” in the expression “if need be.” But it’s an adverb meaning “of necessity” or “necessarily” in “if needs be.” Both expressions have been around for centuries, and are generally used in the sense of “if it’s necessary” or “if necessary.” By far the most common version of the expression is “if need be,” according to Google’s Ngram viewer, which compares words and phrases in digitized books. It’s more common in both American and British English, though “if needs be” appears somewhat more often in the UK than in the US. HBO’s Game of Thrones series is based on A Song of Ice and Fire, a series of fantasy novels by the American author George R. R. Martin. A scene similar to…