To have a worm in one's tongue. To be cantankerous; to snarl and bite like a mad dog.
There is one easy artifice That seldom has been known to miss - To snarl at all things right or wrong. Like a mad dog that has a worm in's tongue.
To worm out information. To elicit information indirectly and piecemeal. To worm oneself into another's favour. To insinuate oneself in an underhand manner into the good graces of another person.
A worm is a spiral instrument resembling a double corkscrew, used for drawing wads and cartridges from cannon, etc.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894