To be captivated; to be held spellbound by pleasing qualities.
Who was the first person to be found enthralling? Strange as it may seem for such a destructive and belligerent race, it was a Viking. The Vikings were stalwart ravagers and pillagers but didn't put much effort into housework. They didn't need to; they had the Thralls.
The Thralls weren't a race as such but a category of people who were at the absolute bottom of the pile in Scandinavian society in the Dark Ages. They were captives of war who were held as slaves, often passing their bondage on to their children. The harshness of the treatment of the Thralls by the Vikings was uncompromising. Thralls weren't allowed to speak in the presence of their masters nor to own property. Anyone captured by the Vikings was said to be 'in thrall' (later 'enthrall') and was in for a very bad time indeed.
Things didn't get much better for the Thralls when Viking dominance faded around 1100 AD. The Catholic Church decreed that enslavement of Christians was sinful, whereas heathens were fair game. This brought about an increase in demand for non-Christian slaves and the Thralls, being mostly Pagans, continued in slavery. The Lindisfarne Gospels, circa 950 AD, makes a mention (in Old English) of a Thrall in the context of 'one whose liberty is forfeit'.
By the 17th century the literal meaning of 'enthrall' had been forgotten and the word began to be used in the way we use it now. Shakespeare used it that way in A Midsummer Night's Dream, 1600:
So is mine eye enthralled to thy shape.
Many Norse words have retained their original negative meanings in modern English - anger, berserk, Hell, irksome, rotten, ugly and troll, for example. It is odd that 'enthralled', a word now associated with pleasure and charm, meant virtually the opposite when it was coined a thousand years ago.