Caloocan was first called Aromahan or Libis Espina by the Spanish colonizers as it
was located in a "libis" (lowland) when it was just a small barrio in Tondo. Its present
name of Caloocan, according to some folk tales, was derived from the Tagalog root
word "lo-ok" (bay) attributed to its nearness to Manila Bay. While others believed that
it came from the word "sulok" (corner) because in the past Caloocan was located at
the corner where the old towns of Tondo and Tambobong (Malabon) met. Hence, the
word Caloocan is a play of the tagalog word "kasuluk-sulokan" (or kaloob-looban)
which means "innermost area".      

    In 1815, Caloocan was separated from Tondo and became an independent
municipality.Its original territory extended to the foothills of Marikina,
San Mateo and Montalban in the east; Tinajeros, Tanza and Tala rivers in
the North; San Francisco del Monte, Sampalok, Sta. Cruz and Tondo in the
south; and Dagat-Dagatan or Aromahan in the west.     

    Eventually, the people of Caloocan turned the historic town into a city through a
plebiscite in 1961, held in accordance with House Bill 6083, which was passed
and approved by both chambers of the defunct Philippine Congress. This led to
the signing of RA 3278 declaring Caloocan as a City in February 16, 1962 by
then President Diosdado Macapagal.