Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pōmērĭum and pōmoerĭum (the first is most freq. in inscrr., the latter in MSS.; but the better manuscripts have also, Varr. R. R. 1, 2, 13, and Tac. A. 12, 23 and 24, pomerium. A third form, post-moerium, Varr. L. L. 5, § 143 Müll., seems merely to have been assumed from the etymology; a fourth archaic form is posi-merium, pontificale pomoerium, qui auspicato olim quidem omnem urbem ambiebat praeter Aventinum … estque prosimerium quasi proxi-murium, pontifices auspicabantur, Paul. ex Fest. p. 248 Müll.), ĭi, n. [post-moerus = murus].
pōmoerium, ii, v. pomerium.