Under French heraldry, it indicates a third son (when they bothered to use cadency on their coats of arms). Since his chances of inheriting the family lands & fortune were low, many of them set out for Charleston to seek their fortune, following the southern branch of the Huguenots.
https://en.wikipedia.org/wiki/Flag_of_South_Carolina
That is part of the reason he did not like them, their loyalty was bought and the "prince" who used them did not have any other leverage. It is difficult to win and then govern with mercenaries as the protectors of the kingdom. A long standing mercenary army does not convey legitimacy, and when disbanded there are issues of proper resettlement and worry about a rival acquiring their service.
Another example is the Janissaries in turkey.
https://en.wikipedia.org/wiki/Facino_Cane
BTW while "taken from their families" is correct, many kept ties with the families. The Sokollu dynasty of grand viziers who practically ruled the empire for decades were taken the same way, but the first of Sokollus, Mehmen Sokollu, was not only able to pass on his position to his relatives, he re-established the Serbian Orthodox Church and got his brother to become its patriarch. We can discuss the humanitarian aspects of this, but practically, these people are not slaves at all; in fact, thinking that these people were slaves is downplaying what a disaster actual slavery is.
PS. There is a book by the Nobel laureate Ivo Andric about exactly the times of Sokollu, that HN readers might find interesting: https://en.wikipedia.org/wiki/The_Bridge_on_the_Drina
My comment was mentioned to highlight that in many practical ways, the Christian population was practically enslaved to the Muslim overlords (regardless whether them being "real" Turks, or, more commonly, local converts, or even Janissaries). Much more than a Christian serfdom was a lightweight variation on slavery.
Christian population as a whole had very little to choose whether their children will be taken away and become Janssaries, at least until late times, and once taken away, those people had very little influence about their career choices. They were slaves in all practical ways the slavery means. For some exceptions, that slavery turned out to lead to high positions (like Sokollu) but, on the other hand, if the subject population retained their independence, talented people like Sokollu might have had opportunity to build up their local communities/states, instead of conquering the world for Ottoman sultans? :)
PS. I am personally an atheist, so I do not tend to look at the things here from the Christianity: right; Islam: wrong perspective.
I mean, finding cases of African American slaves that lived and worked as cooks or home attendants, or nannies, or whatever easier jobs were available in the South, in addition to much harder cotton picking would not be an argument that those people were not enslaved. The fact that one does not literally carry chains the whole day does not mean that he is not a slave, if the owner can literally decide on the life and death, without much consequence.
If we talk about imperial dominance in Ottoman Balkans, I would accept that local Muslim population (largely converts) lived under imperial dominance. Christian peasants - much, much heavier.
The Norse themselves still tended to follow partitioning laws, at least until the Scandinavian kingdoms started to coalesce. The repeated invasions of England between Ethelred the Unready and the final conquest of William the Bastard were not driven by second sons needing kingdoms for themselves, it was driven by England having the best tax base in the North Sea but high political stability, as well as the dying out of family lines.
Key point about the latter: when Edward the Confessor died without issue, the claims to the English throne were:
* Edward's brother-in-law and most powerful vassal, Harold Godwinson (son of the person who put Edward on the throne in the first place)
* William, the bastard son of Edward's maternal cousin. Bolstered by "when he was staying over when he was young, he totally promised me the throne when he died."
* Harald Hardrada, whose claim is "Cnut was King of England. He died, so his claim passed to Harthacnut. Harthacnut and Magnus made an agreement that, should one die without issue, the other would inherit his lands. Harthacnut died without issue, so Magnus should have been King of England. Magnus died without issue, so his claim winds its way back to me, his father's half-brother by way of mother."
Third sons wouldn't starve to death in any case, but they would rattle around the family lands making a nuisance of themselves and borrowing money from Dad. Noble families got some income from their tenants' taxes, generally, but it wasn't always enough to maintain yourself in high style. In some times/places, noblemen could get involved in trade, but that would mean funding other people's endeavors, not becoming merchants themselves. And sometimes even that was restricted or frowned upon.
In essence him being a crafts-person or merchant would have been looked down on by everyone.