You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Ashkenazi_Jews

Context:
Speculation that the Ashkenazi arose from Khazar stock surfaced in the later 19th century and has met with mixed fortunes in the scholarly literature. In late 2012 Eran Elhaik, a research associate studying genetics at the Johns Hopkins University School of Public Health, argued for Khazar descent in his paper The Missing Link of Jewish European Ancestry: Contrasting the Rhineland and the Khazarian Hypotheses. A 2013 study of Ashkenazi mitochondrial DNA found no significant evidence of Khazar contribution to the Ashkenazi Jewish DNA, as would be predicted by the Khazar hypothesis.

Question:
When did the idea that the Ashkenazi may have come from Khazar stock come about?

in the later 19th century