The Oxford Dictionary of English  tells me that a delinquent is a young person prone to commit minor crimes.

The term juvenile delinquent makes this a little more specific.

I see from the mothership, the Oxford English Dictionary that the sense of “a petty criminal” has been effect since the first appearance of the word in English back in 1484; this from the presses of William Caxton, England’s first printer.

But before delinquent was an English word it had been a Latin word.  There too it had meant someone who offended.  But the deeper Latin root is a word linquere that didn’t mean anything at all like “a young tough.”  Instead it meant “to leave” and this is a meaning that traces back to Indo-European.

I can think of two possible reasons why a word meaning “gone-outa-here” might grow to mean “‘a crook.”

One could be that the person just wasn’t where they were supposed to be when they were supposed to be there.  For example someone who is delinquent in repaying a loan just didn’t show up to pay it, or the expected money didn’t show up.

The other reason might be that the guy who did the crime didn’t want to do the time and so he linquere-ed out of there as fast as his little legs would carry him.  When you see someone leaving the scene of a crime, you automatically think of them as the culprit.

The etymological sources I looked at don’t reach far enough back in enough detail to tell me if either of these suppositions might be true.

The OED entry for delinquent hasn’t been updated yet in the effort to issue the Oxford English Dictionary Third Edition, so the most recent citation in there is from 1891 and there isn’t much about juvenile delinquents.

But I do see a citation from Washington Irving referring to a “delinquent school-boy.”

Washington Irving was an early—if not the first—celebrity author that the United States produced.  He died in 1859 and from what I see of him he was not only a great writer but also a really nice guy.  With his success came support for other writers.

One day he had a chance meeting with another writer who was particularly interested in what Irving was working on for his next book. The reason was that an earlier Washington Irving book had been on the history of Spain and this other writer had been a little disappointed when it came out because his own book included some of the same information and hit the bookstores only a few months afterward; he didn’t want it to happen again.

Washington Irving says:

“Are you writing about something American?”

The other guy says “yes.”

“Is it about the Conquest of Mexico?” says Irving

“Yes” quavers the other guy.  To which the big hearted Irving replies:

“Well then, I am engaged upon that subject, but I abandon it to you.”

One more thing about Washington Irving; his Spanish History was considered so authoritative that four years later he served as the US ambassador to Spain.  Which of course forced him to linquere America for a while