More of a history question... I understand です became more commonly used in late Edo, but before that (as I understand) it was commonly associated with low-society life, such as prostitutes and thieves as portrayed by theatre during the earlier era. So how did one of the most essential grammatical elements of contemporary Japanese language come to overtake the former standard?


です did not overtake なり. だ did.

なり is merely a basic connective, "A is B," without any specific implications for the formality level or politeness of speech. Etymologically, it is a fusion of に+あり "exists" (where に is not the locative particle, but the 連用形 form of the copula "to be"), thus A, B なり means literally "A, being B, exists." Later, following the general trend of Japanese that attaching a 連用形 of a verb directly to another verb to denote a sequence gives way to attaching the verb through the -て-form (all the multiple て-attachments of the modrn language, like ている, てある, てくる, etc. are very recent), にwas gradually replaced by its own て-form, にて > で. Thus なり was turned into である [Note 1], shortened to じゃ or だ.

です is a totally different beast, as it is, forst and foremost, a polite form. It did not replace なり, but it replaced many of its predecessors, which frequently co-existed. While Classical Japanese had 敬語, there was no direct analogue to the current です/ます forms, which do not serve any honorification, but just state that the whole sentence is polite. Post-Classically, however, such forms started to emerge. [候]{そうろう} was, I believe, prominent enough in this position to have a whole style of writing ([候文]{そうろうぶん}) named after it, and when you attach そうろう to で (analogically to how you attach ある to で in order to make である), you get でそうろう, which slowly withers down to でそう and then です [Note 2]. Only in the early 20th Century, when modern literary language was being formalized, です was chosen above its competitors, such as であります, でいらっしゃいます, でございます, presumably for being shorter.

[Note 1] あり became ある because of the general phenomenon called "the final/adnominal merger."

[Note 2] This is not the only hypothesis as to how です was formed, but, in my opinion, the most probable one. The alternate, namely, that です is short for であります/でございます and its friends, does not impress me, as all these forms, when uttered, have a very strong emphasis on the あ in the penultimate syllable, and it is unclear how could the contract to something with the vowel え.

  • '...but the 連用形 form of the copula "to be"...' <--- I thought なり is the copula "to be"? So if に was the 連用形, what was the 終止形/plain form? – Sweeper Apr 20 '20 at 14:13
  • The copula is very defective in paradigm; I believe it only has a 連用形 and a 連体形, the last being の; it is still around, as the の which does not express fenitive but equality (the 部長の田中 "Tanaka being 部長" one). That's why it was forced to attach あり in order to produce a form that it could not form on its own, namely, a 終止形. It is the same as when the copula of adjectives, く, becomes かり or ず becimes ざり for any more or less complex form. By the way, the copula could have an あり-style 連体形 as well, and this still remains, as the な that gives the name to な-adjectives. – Alexander Z. Apr 20 '20 at 15:44
  • There are multiple lines of derivation for です, with one of the more common being a shift from でござります. More at Kotobank. Re: vowel shift from the medial //a// that you mention, see also intermediate form でげす. Note that the でそうろう derivation may be limited to 狂言. – Eiríkr Útlendi Apr 20 '20 at 18:22
  • Very interesting answer, do you happen to know good books on the subject? – wip Apr 20 '20 at 19:16

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