billyboy
Noun
Meaning
A flat-bottomed river barge or coasting vessel.
Source: Webster's dictionaryExamples
The policemen who come to Alex's rescue turn out to be none other than Dim and former gang rival Billyboy.
Early on in the story, Alex and his droogs battle Billyboy and his droogs, which ends abruptly when the police arrive.
Later, after Alex is released from prison, Billyboy (along with Dim, who like Billyboy has become a police officer) rescue Alex from a mob, then subsequently beat him, in a location out of town.