The Gnomish Lexicon of the 1910s had G. ûmi “large” (GL/75). It was clearly related to ᴱQ. ūmea “large” from the contemporaneous Qenya Lexicon (QL/97), though neither word had a well-defined root.
Gnomish
beleg
masculine name. Beleg
beleg
adjective. mighty, great
tuor bo-beleg
Tuor bo-Beleg
baldrin
adjective. mighty
polodrin
adjective. mighty
ûmi
adjective. large
A word appearing as G. polodrin “mighty” in the Gnomish Lexicon of the 1910s, an adjective form of G. polod “power, might, authority” (GL/64). It had an archaic variant {poldurin >>} †polurin or polorin which was sometimes used as a sobriquet for Tulcus.
Neo-Sindarin: Since ᴹ√POL(OD) still had to do with “strength” in Tolkien’s later writings, I’d adapt this word as ᴺS. polodhren “mighty, ✱powerful” for purposes of Neo-Sindarin using the later Sindarin adjective -ren. Given the meanings of its base noun (including authority), I’d assume this adjective has a connotation of political power. I’d constrast it with S. belaith which I’d use for “mighty” in general (independent of authority).