surregulus
Could not find subregulum in Logeion dictionaries.
subregulum Noun: masculine genitive plural, Noun: masculine accusative singular of surregulus
sur-rēgŭlus (subr-), i, m.,
- a petty prince, a feudatory vassal, Amm.17, 12, 21; Sulp.Sev.Hist. Sacr. 2, 10, 1.