The Talmud [Berachot 26b] gives two opinions about the origin of the daily prayers:
Prayers replace two daily sacrifices in the Temple.
Prayers are composed in honor of the forefathers Abraham, Isaac and Jacob.
In addition to the Karaites, according to some sources, some Jews of Europe prayed twice a day.
If there was such a custom, then what were these prayers?
"Rabbi Alfasi ruled that maariv or evening prayers were henceforth to be considered an obligatory prayer service. Traditionally maariv was regarded as an optional service, as it did not correspond to the tamid offering of the Temple ritual which took place only in the morning and afternoon. The Karaites thus prayed twice a day corresponding to the Temple sacrifices, and Rabbi Alfasi wanted to disconnect from these Karaite customs. Interestingly enough, the Jews of France and Germany, where there was no Karaite presence, continued to pray only twice a day."