Someone was reading up on their California history when they named those streets!
Castec is a variant spelling of an old California/Mexican/Chumash
Indian name -- Castac or Kashtiq.
You can see a reference to the Castec/Castac spellings here, on this
19th century map:
Plan del paraje conocido bajo el nombre de Castec
Subject: Rancho Castac
Note the variant spellings. Click on the map image to see a larger
picture, if you'd like.
mentions the Chumash spelling:
"...As we know, Castac is derived from the Chumash name Kashtiq (John
Johnson, The Trail to Kashtiq, Journal of California Anthropology,
1978) and the name occurs in the oldest records..."
and there's a bit of history of land grants with the Castac name:
...Between 1824 and 1846, Mexican governors authorized a series of
land grants in California that would ultimately come to form the
Rancho El Tejon (Magruder 1950). Rancho Castac, consisting of 22,178
acres, was granted by Governor Manuel Micheltorena on November 22,
1843 to Jose Maria Covarrubias. Governor Micheltorena granted rancho
El Tejon to Jose Antonia Aguirre and Ygnacio del Valle on November 24,
...Edward Beale was responsible for the creation of the Tejon Ranch
during the American period. In 1865, he began amassing his land empire
through the purchase of Mexican land grants including: La Liebre, Los
Alamos, Agua Caliente, Rancho Castac, and Tejon.
and a bit more history here:
The Tejon (pronounced 'TAY-yohn') Ranch traces its existence back to
the late 18th century. Europeans first set foot on the land when the
Spanish soldiers crossed the Tehachapi Mountains hunting for
deserters. The name 'Tejon'--Spanish for 'badger'--was first
reportedly used when troops found a dead badger in the entrance to a
canyon in the area. In 1843 the Mexican government made grants for the
land that became three ranches: Rancho los Alamos y Agua Caliente
(Cottonwoods and Hot Water Ranch); Rancho el Tejon (Badger Ranch),
Rancho de Castec (Eye Ranch). A fourth tract, Rancho la Liebre (Rabbit
Ranch), was granted in 1846. Those four ranches would later be joined
together to form the Tejon Ranch.
Santa Clarita Valley
A Timeline of Historical Events
1843 -- November 22: Rancho Castac (Castaic) granted to Jose
Covarabias [spelling per deed].
Note that there's an El Tejon Way just a few streets north and west of
I trust this information fully answers your question.
However, please don't rate this answer until you have everything you
need. If you would like any additional information, just post a
Request for Clarification to let me know how I can assist you further,
and I'm at your service.
All the best,