a·bet / əˈbet/ • v. (a·bet·ted, a·bet·ting) [tr.] encourage or assist (someone) to do something wrong, in particular, to commit a crime: he was guilty of aiding and abetting the murderer. ∎  encourage or assist someone to commit (a crime): we are aiding and abetting this illegal traffic.DERIVATIVES: a·bet·ment n.a·bet·tor / əˈbetər/ (also a·bet·ter) n.ORIGIN: late Middle English (in the sense ‘urge to do something good or bad’): from Old French abeter, from a- (from Latin ad ‘to, at’) + beter ‘hound, urge on.’

ABET

To encourage or incite another to commit a crime. This word is usually applied to aiding in the commission of a crime. To abet another to commit a murder is to command, procure, counsel, encourage, induce, or assist. To facilitate the commission of a crime, promote its accomplishment, or help in advancing or bringing it about.

In relation to charge of aiding and abetting, term includes knowledge of the perpetrator's wrongful purpose, and encouragement, promotion or counsel of another in the commission of the criminal offense.

A French word, abeter—to bait or excite an animal.

For example, the manager of a jewelry store fails to turn on the store's silent alarm on the night she knows her cousin plans to rob the store. Her conduct is that of abetting the robbery. If, however, she merely forgot to turn on the alarm, she would not have abetted the crime.

The word abet is most commonly used as part of the comprehensive phrase aid and abet.

abet incite (now, to wrongdoing). XIV. — OF. abeter, f. a- AD- + beter BAIT.
So abetment XIV.