According to the County of Los Angeles Public Library website: The name Agoura Hills originated in 1928 when the last name of well known local French shepherd Pierre Agoure, was selected as the name of the city in order to establish a permanent post office in the community. However, the "e" became an "a" for unknown reasons, either due to an error or perhaps for ease of spelling. We may never know.
History repeats itself. A few weeks ago, Bonnie Q posted a photo of the above sign on the CVG Facebook page and earlier this week I had to see it for myself earlier this week. While it is not exactly something that a spellchecker would catch, how Caltrans let this typo make it to the 101 freeway is a bit puzzling. This sign can be seen on the 101 eastbound between Lindero Canyon and Reyes Adobe Road.