Ancient writers believed that the worship of Terminus had been introduced to Rome during the reign of the first king Romulus (traditionally 753–717 BC) or his successor Numa (717–673 BC). Modern scholars have variously seen it as the survival of an early animistic reverence for the power inherent in the boundary marker, or as the Roman development of proto-Indo-European belief in a god concerned with the division of property.
These rites were practised by private landowners, but there were also related public ceremonies. Ovid refers to the sacrifice of a sheep on the day of the Terminalia at the sixth milestone from Rome along the Via Laurentina; it is likely this was thought to have marked the boundary between the early Romans and their neighbors in Laurentum. Also, a stone or altar of Terminus was located in the Temple of Jupiter Optimus Maximus on Rome's Capitoline Hill. Because of a belief that this stone had to be exposed to the sky, there was a small hole in the ceiling directly above it. On occasion Terminus' association with Jupiter extended to regarding Terminus as an aspect of that god; Dionysius of Halicarnassus refers to "Jupiter Terminalis", and one inscription names a god "Juppiter Ter."
There is some evidence that Terminus' associations could extend from property boundaries to limits more generally. Under the Republican calendar, when the intercalary month Mercedonius was added to a year, it was placed after February 23 or February 24, and some ancient writers believed that the Terminalia on February 23 had once been the end of the year. Diocletian's decision in 303 AD to initiate his persecution of Christians on February 23 has been seen as an attempt at enlisting Terminus "to put a limit to the progress of Christianity".
The stone in the Capitoline Temple was believed to have been among the altars located on the Capitoline Hill before the Temple was built under Tarquinius Priscus (traditional reign 616–579 BC) or Tarquinius Superbus (535–510 BC). When the augurs took the auspices to discover whether each the god or goddess of each altar was content for it to be moved, Terminus refused permission, either alone or along with Juventas the goddess of youth. The stone was therefore included within the Capitoline Temple, and its immovability was regarded as a good omen for the permanence of the city's boundaries.
This view of Terminus retains some recent adherents, but other scholars have argued from Indo-European parallels that the personalised gods of Roman religion must have preceded the city's foundation. Georges Dumézil regarded Jupiter, Juventas and Terminus as the Roman form of a proto-Indo-European triad, comparing the Roman deities respectively to the Vedic Mitra, Aryaman and Bhaga. In this view the sovereign god (Jupiter/Mitra) was associated with two minor deities, one concerned with the entry of men into society (Juventas/Aryaman) and the other with the fair division of their goods (Terminus/Bhaga).