rumusculus.

From rūmor (“gossip; rumor”) + -culus (diminutive-forming suffix). (Like other abstract nouns ending in the suffix -or m, the word rūmor originally had a nominative form ending in *-ōs and an oblique stem ending in *-os-: the form rūmusculus would be regular if built on the original oblique stem. Alternatively, the ending -usculus may have been taken by analogy from older diminutives such as arbuscula (“a small tree”) (from arbor), meliusculus (“a little better”) (from melior, melius, meliōr-), or other diminutives of comparative words. The earliest attested use of rūmusculus is in Cicero, who probably used the innovative nominative form rūmor, and certainly used the innovative oblique stem rūmōr-.)