Does the phrase "begging the question" make any sense?

I know what "begging the question" originally means, but I just can't make any sense of the idiom. The phrase really seems to have nothing to do with its own meaning.

The original Latin phrase, petitio principii, is often translated as "assuming the initial point," which quite simply explains the practice.

Does the phrase "begging the question" carry any meaning (related to what it's used for)?

One of the meanings of beg, according to the Oxford English Dictionary, is "to take for granted without warrant." The OED notes that this meaning is most common in the phrase to beg the question, and indeed all of the citations for this meaning are of similar, though not identical, phrases. Ignoring a few duplicates, here are those citations:

1581 W. Charke in A. Nowell et al. True Rep. Disput. E. Campion (1584) iv. sig. F f iij, I say this is still to begge the question.

1680 Bp. G. Burnet Some Passages Life Rochester (1692) 82 This was to assert or beg the thing in Question.

1687 E. Settle Refl. Dryden's Plays 13 Here hee's at his old way of Begging the meaning.

1852 H. Rogers Eclipse of Faith (ed. 2) 251 Many say it is begging the point in dispute.

The etymology of beg is no more helpful—in fact, it's hotly disputed. Some believe that it came from the Old English word bedecian, which in fact means "to beg," but that word has only been found once in all of the surviving Old English literature, and no clear links beyond its meaning and a very slight phonological similarity have been found between it and beg. Others say that beg came, via Old French, from the Latin begardus or beguin, a Christian lay mendicant order known in English as Beghards and Beguines. Either way, there's no clear connection to the meaning of beg used in beg the question.

What we're left with, then, is this: beg in this phrase means something like "to take for granted without warrant," but it only has this meaning in this and very similar phrases. It seems to have acquired this meaning sometime in the late sixteenth century, but how that happened is a mystery.

Looking at a Latin dictionary, petitio usually means a requesting, asking, desiring, petition, solicitation. The word principii is the genitive declension of principium, which means beginning, commencement, origin. So petitio principium means a petition of the beginning, or an appeal to the thing you started with.

Here the thing you started with is the point you were trying to make, or the question. An appeal to it essentially means assuming it. So petitio principii means assuming the point you were trying to make, or "appealing to the question". However, begging is another translation for petitio. Using this word rather than appealing to, we get "begging the question". Since begging does not have the connotations that appealing to does in English, it is really an inferior (I would even say incorrect) translation.

How did begging the question become the accepted translation for petitio principii? Maybe it started out as a joke. I can't answer this.

ADDED: There is a Language Log blog post that discusses the phrase "begging the question", and goes into more detail.

The actual story about "beg the question" is far more complicated than virtually all authorities suppose. In its logician's use: it is always used absolutely, that is, "That just begs the question" (full stop: there's no further "question"). In that sense, it means "Assume the very thing you're trying to prove."

That is, of course, a bizarre construction, and it is only explainable on the basis of its historical origin, which descends from a phrase in Aristotle's logical works that can't really be understood without knowing the context in which it arose: a dialectical argument as portrayed in Book VIII of his Topics. As depicted there, a dialectical debate has two participants, a questioner and an answerer; the answerer begins the debate by undertaking to defend some proposition, and the questioner then tries to refute the answerer by asking questions that can be answered by yes or no of the answerer and, from these, deducing the contradictory of the answerer's initial proposition. In this context, Aristotle calls the initial proposition proposed by the answerer "the initial thing" (to en archêi).

One of the rules of this kind of debate is that the questioner cannot simply make the very thesis put forward by the answerer into a question and ask that: to do so is the error of "asking for the initial thing" (to to en archêi aiteisthai). It also counts as "asking for the initial thing" if the questioner asks something not identical to but more or less equivalent to the initial thing, though explaining how close it has to be is a problem for Aristotle.

Translated out of the context of dialectical debate, this same error can be described as "taking the conclusion you are trying to prove as one of the premises of your argument", and that is the original sense of "begging the question" when it enters English in the late 16th century ("question" having taken on the sense "the proposition being debated").

A complicating point in this history is that the Greek verb aitein, "ask", took on the sense "ask for as a premise" in logical and mathematical contexts and thus came to mean "assume" (as a premise). If we assume the same for "beg" in English, then "beg the question" can indeed be read as "assume the thing you're trying to prove", although that is hardly what an ordinary speaker of English would suppose it to mean.

(As a footnote: the translation "in the beginning to assume", given in some authorities as a translation of to en archêi, is grammatically impossible as a rendering of it in Aristotle, since it assumes the definite article to goes with the infinitive aiteisthai; Aristotle's usage, especially in those contexts in which the phrase begins with two definite articles, shows that it goes instead with "in the begining" (so, "to assume the in-the-beginning thing" would be much better).)

One possibility that I don't see considered is that the phrase is connected to 'beggar belief', which roughly means to defy belief (something can also beggar description, which means to defy attempts at description). This is more or less exactly the same meaning as 'beg the question' - namely defy the question, by presupposing an answer. I find it doubtful that this is a coincidence. All that would need to happen to get the word 'beggar' into the phrase 'beg the question' would be to shorten it - one of the most common transformations of a word over time.

If this is plausible (as it seems to me) the 'beg the question' would have the same origin as 'beggar belief' or 'beggar description'. A possibility there is that it comes from Shakespeare, in Antony & Cleopatra, 1616:

For her owne person It beggerd all discription.

The word 'beggerd' here is understood to have meant something like 'dispossessed' - to be beggered was to be dispossessed of ones belongings. In that case, the origin of 'beg the question' would be 'beggerd the question' which would mean to have been dispossessed of the question, by having presupposed the answer.