The idiom is a mistranslation of petitio principii, which is the Latin phrase meaning to assume the intended point, and which itself is a 16th-century mistransl

The idiom is a mistranslation of petitio principii, which is the Latin phrase meaning to assume the intended point, and which itself is a 16th-century mistranslation of Aristotle from around 2,300 years ago, so it’s a wonder that anyone still understands this phrase at all. I recommend treating this phrase, “to beg the question”, as an irregular verb. The component words provide the inflections, but not the meaning, although there may be some poetic utility.