"It seems there is none" is なさそう, which escapes the usual rule for 形容詞 (イ-adjectives), which says "drop the い and add そう".
Is there a historical explanation for this exception? And does it have anything to do with なさいません?
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.
Sign up to join this community"It seems there is none" is なさそう, which escapes the usual rule for 形容詞 (イ-adjectives), which says "drop the い and add そう".
Is there a historical explanation for this exception? And does it have anything to do with なさいません?
Your "usual rule" is incomplete. It should be:
Hence, nai:
atui:
Well, in first place there are possible confusions depending you are referring to ない as a [助動詞]{じょどうし} or 無い as a [形容詞]{けいようし}.
In the case of "It seems there is none", なさそう will be 無い adjective [連用形]{れんようけい} + そうだ [助動詞]{じょどうし}。
It seems that when そうだ was first introduced at Muromachi period, なそう was used but as な is only one syllable, さ was added through time.
It has nothing to do with なさいません which is the negative form of [為]{な}さる verb.
For information, in the case of ない as a [助動詞]{じょどうし}, なそうだ is used:
彼はお酒を飲まなそうだ。
But recently, さ is sometimes added:
彼は来な(さ)そうだ。