The Japanese word for shoplifting is manbiki, usually written 万引き. That would mean something like "pulling ten thousand" (or "drawing a myriad" in early 20th-C. translatorese) -- if it represented the actual etymology, which of course it doesn't.

Instead, the word seems to have sprung from Edo-accented pronunciation of mabiki, a nominalized form of the verb mabiku (間引く), "pull out [something] in between". You might do this to still-growing vegetables, for example -- pull a few out of the row to make space for the others. (Or you might do it to children on the same principle.)

That's all satisfying and well and good, but then what about the contemporary Kansai counterpart to the word, mangai (万買い, "man purchase")? Did they borrow the Edo term and replace hiku with kau? If so, why would they do that? If not, does their man mean something different?

None of my books even venture a guess, but MAKIMURA Shiyō's Encyclopedia of Osakan language (大阪ことば事典) does record a word man meaning "opportune moment", "chance", "fortune" (probably related to the same ma 間 in 間引く, via its extremely broad semantic range: gap, pause, beat, space, period...). So that could be an easy source for mangai: "'buying' at a favorable moment".

(I should note that I can find sources who claim that this is the man to be found in manbiki, although modern scholarship seems to prefer the explanation two paragraphs above -- I just can't find anyone addressing mangai specifically.)

Bonus word: dejitaru manbiki, "digital shoplifting", a term invented by the Japanese Magazine Association (日本雑誌協会) and Telecommunications Carriers Association (電気通信事業者協会) in 2003 to denounce the practice of using your cellphone to take photos of magazine or guidebook articles in the store for later reference, instead of actually purchasing the entire product as would have been necessary in the olden days.

Self-promotional addendum: My translation of HIRATO Renkichi's poem "Fish" is up at Néojaponisme.