What was the language Zamenhof dreamt in when finding the solution for a/the definite article "la" in his Esperanto?
What was Zamenhof's "first" language?
(quoted from the Mendele list vegn mame-loshn --mi'e .aulun)
     "I thought that the recent postings on the topic of language in dreams
      had pretty much covered the range of phenomena in existence on this
      topic, but it appears that I was wrong.  I was recently browsing
      through a biography of Zamenhof, the creator of Esperanto, called
      "L'homme qui a défié Babel"(the man who defied Babel) by René
      Centassi and Henri Masson, when i came across an account of a dream
      which Zamenhof had, apparently at the age of about 16.  That would
      have been more than 10 years before 1887, usually considered the
      birthyear of the language, when his first grammar of Esperanto was
      published.  He at that time was concerned with the question of whether
      his language should have a definite article, having noticed that his
      own Polish, and also Russian (presumably the prestige language of that
      time and place, since Zamenhof lived in Bialystok, then part of the
      Russian Empire), did not.  In the dream he was pondering this question
      near a forest with his uncle Jozef and his Greek teacher, whose name
      was Billevitch.  Zamenhof suggested that they might find someone in
      the forest who could help them. Billevitch, on the contrary, warned
      against going into the forest on the grounds that there were three
      girls in red who wanted to harm them.  Zamenhof then looked toward the
      forest, saw the girls in question, and cried out, "there are
      - -the-(author's emphasis) three girls in red."  Zamenhof then woke up
      in a sweat, but decided that his problem had been solved.  The
      definite article had in his view proved its usefulness.  And, as every
      Esperantist knows, there is a definite article, namely the invariable
      "la". I can't remember having or hearing about a dream with this degree of
      linguistic specificity.  It is also not clear what language the dream
      occurred in.  Probably not Polish or Russian, since these lack the
      article which played such a prominent role. Zamenhof knew several
      other languages, most of them with definite articles, so these appear
      to be better candidates.  In any case, postings from others suggest
      that people can dream in languages that they don't know very well.
      The last possibility is that the language was some embryonic form of
      Esperanto itself, since Zamenhof was so intensely concerned with this
      topic.
      D.M.
      E. P. asked about whether L. L. Zamenhof, the
      inventor of Esperanto, knew Yiddish. Although he apparently regarded
      Russian as his first (and favorite) non-invented language, he clearly
      was a speaker of Yiddish and, in fact, wrote a fascinating grammar of
      Yiddish in Russian. The grammar was not published until 1982 with the
      original Russian and a complete Esperanto translation. In it Zamenhof
      argued for Latinization of the Yiddish writing system. He proposes a
      literary pronunciation that is almost exactly the same as the YIVO norm.
      A propos of another thread he states that one should spell 'auf' as
     'af.' His proposed spelling norms totally reject the daytshmerish
      orthography in favor of one reflecting actual Yiddish pronunciation. He
      calls for a purging of daytshmerisms from the language. All in all, a
      very "modern" approach for 1879-1882, the approximate time of
      composition.
      I don't know about the 'the,' but it is widely accepted that only one
      purely Yiddish morpheme made it into Esperanto. This is the suffix (now,
      basically, substantive) -edz-o 'husband,' which is viewed as a back
      formation of -edz-in-o 'wife,' and which appears to derive from the
      suffix -etsn in the word rebetsn.
      By the way, Zamenhof's writings on Yiddish are collected in: Adolf
      Holzhaus. "L. Zamenhof, Provo de gramatiko de novjuda lingvo- kaj
      -Alvoko al la juda intelektularo. Helsinki, 1982.
H. I. A.
      According to Reyzen's _Leksikon_, Zamenhof's father, Marcus, and his
      grandfather, Fabian, were both teachers of French and German in
      Bialystok, then part of the Russian empire, where four
      languagesRussian, Polish, German and Yiddishwere common. Reyzen says
      nothing about his first language, but points out that Zamenhof once
      thought that Yiddish, because of its widespread character, might serve
      as a basis for an international language. Zamenhof spent three years
      working on a Yiddish grammar, only fragments of which were ever
      published (in a Yiddish periodical). In his publications on Yiddish he
      suggested adopting the Latin alphabet for Yiddish.
      In 1958 the editor of _Yidishe shprakh_, Yudel Mark, gently
'corrected a reader who had asserted that Zamenhof's mother tongue was Russian' (emphasize by me)
      He argued that Zamenhof grew up in a bilingual milieu even if he learned
      Russian as a child and heard Russian at home--and from his mother at
      that (YS 18:80).
      In a subsequent issue of the journal (YS 19 1959:30) another reader
      expressed his surprise that Zamenhof had written for a Yiddish
      periodical and worked on the language.  He related his own experience of
      being visited daily by Dr. Zamenhof (who was an ophthalmologist) during
      the four weeks in 1902 when he was a patient in a Jewish hospital in
      Warsaw.  He reported that the doctor normally used Polish while making
      his rounds, but since he (the patient) spoke little Polish, Zamenhof
      spoke "a 'daytshn' yidish" with him.  He added that the doctor "(hot)
      ober keyn mol nit oysgeredt keyn ekht yidish vort."  The editor (Mark)
      conceded that this may have been true, but suggested that the strongly
      anti-Yiddish attitude of the time would have made it difficult for a
     doctor to deal officially with his patients in ordinary Yiddish, "nit
     fardaytshndik a bisl zayn shprakh."  Mark added that it is conceivable
     that a person could perfectly well write about linguistic matters in
     Yiddish without being a fluent _speaker_ of the language.
B. R."