the.com/shilling

means To promote or plug something (often a product, cause, or person) with persistent enthusiasm, usually for payment or personal gain.

from The verb rides on the noun shilling, an old British coin — itself of uncertain origin, possibly related to a Germanic root meaning 'to sound' or 'to divide,' as in dividing a larger unit of currency. The modern sense of 'shilling for' something emerged from 'shill,' a 20th-century American slang term for a con artist's hidden accomplice who talks up the goods or places the first bet to lure in marks. That shill is likely a shortening of 'shillaber,' of obscure carnival and underworld origin. The coin and the con converged in the verb 'shilling,' now used for anyone — paid or not — pushing something a little too eagerly.