begyoudaoicibaDictYouDict[beg 词源字典]
beg: [OE] Beg first turns up in immediately recognizable form in the 13th century, as beggen, but it seems likely that it goes back ultimately to an Old English verb bedecian ‘beg’. This came from the Germanic base *beth-, from which English also gets bid.
=> bid[beg etymology, beg origin, 英语词源]
beg (v.)youdaoicibaDictYouDict
c. 1200, perhaps from Old English bedecian "to beg," from Proto-Germanic *beth-; or possibly from Anglo-French begger, from Old French begart (see beggar). The Old English word for "beg" was wædlian, from wædl "poverty." Of trained dogs, 1816.

As a courteous mode of asking (beg pardon, etc.), first attested c. 1600. To beg the question translates Latin petitio principii, and means "to assume something that hasn't been proven as a basis of one's argument," thus "asking" one's opponent to give something unearned, though more of the nature of taking it for granted without warrant.