Questions about 背負う

Question

背負う is pronounced せおう, but many dictionaries also list a second pronunciation as しょう.

1. I've never heard it pronounced as しょう in practice. In what situations does it have this pronunciation? Is that only an archaic pronunciation, or is it still in use? Is it a regional/dialectical thing? Is one free to pronounce it with either way, unrestricted?

2. せおう (or おう, rather) conjugates as a 五段. Does しょう also conjugate as a 五段?

• ます形　→　しょいます
• ない形　→　しょわない
• ～て･た形　→　しょって・た
• 命令形　→　しょえ
• 仮定形　→　しょえば
• 可能形　→　しょえる
• 意志形　→　しょおう

Answer 1

The only difference I perceive is that しょう sounds slightly more "intimate" as if it's a regional dialect. But this doesn't mean せおう is less of everyday language. Probably I feel this way because the pronunciation is a naturally slurred version of せおう (i.e., /seo/ -> /syo/), which is most likely the result of a natural sound shift like 音便.

The tricky thing is that しょう here is not a homonym of しょう as in 賞, 章, and 小. While they look exactly the same in kana, しょう as 背負う does not have the double mora お. It's しょ as one mora plus う as another mora, i.e., it's not the same pronunciation as しょー.

As for its conjugation, it's 五段 as you guessed.

Answer 2

One can hear しょって used often when talking about rucksacks or backpacks.

リュックサックを[背負]{しょ}って[歩]{ある}く

There isn't really much difference (しょう pronunciation is from せおう anyway), though, and people use them quite interchangeably. Though, sometimes the nuance of しょう can be such that it is [迷惑]{めいわく}...

However, there is one situation, when one's talking about someone being vain or full of themselves, where one can use しょってる and not せおってる. One hears this usage often in [落語]{らくご}...

Answer 3

Addendum: Pronunciation

The verb 背負う has two modern pronunciations: せおう, and しょう. From a modern perspective, it's a little befuddling how these two interrelate. If we look at the past, however, the story comes clear.

The version starting with し is sometimes analyzed by modern speakers as the し being a slurred or otherwise shifted pronunciation of せ. However, historically, it is worth noting that せ was itself formerly pronounced more like //ʃe// (as in English shed). The non-fricative sibilant //se// version appears some time after the 1603 日葡辞書 (Nippo Jisho, "Japanese-Portuguese Dictionary"), where all of the せ sounds are spelled ⟨xe⟩ instead -- and where that ⟨x⟩ was the Portuguese spelling at the time of the "sh" sound in modern English (more or less -- for strict phonologists, I'm uncertain if that was the voiceless postalveolar fricative [[ʃ]], the voiceless alveolo-palatal fricative [[ɕ]] as in modern Tokyo Japanese, the voiceless retroflex fricative [[ʂ]] (unlikely, I think), or some other specific phone). Note all of the entries in the X antes do E section ("X before E") starting from the bottom right of this page, including such otherwise-familiar terms as "Xecai. Mundo." (Sekai. World.)

So the difference in reading between せおう and しょう is not a seemingly arbitrary rearrangement of consonant and vowel values, but instead the unsurprising result of a contraction, as //ʃeou// shifted to just //ʃou//.

According to the 日本国語大辞典【にほんこくごだいじてん】 entry here at Kotobank, the shorter しょう reading appears first in 1278, well within the time period when せ was still pronounced as a fricative //ʃe//, and thus a contraction from //ʃeou// to //ʃou// would not have been all that exceptional.