This ambivalent word seems to have taken on its meaning of a personal attribute in the late 19th century, although Shakespeare uses the plural charms to describe attractive features.
It does not derive from the misleadingly similar word χαρμή, which Homer uses to denote the joy of fighting in battle: that is a formation from χαίρειν, to rejoice. No, charm derives from the Latin carmen in its sense of a spell or incantation—used, for instance, in Aeneid IV, 487-8, where Dido describes the power of a mysterious African priestess from Ethiopia:
haec se carminibus promittit solvere mentes
quas velit, ast aliis duras immittere curas…
¶ This woman promises with her spells
to set free the minds of whom she wishes,
but on others to cast cruel sorrows…
Not even in Greek, and certainly not in Latin, can be found the nuances that attach to such English expressions as charming, fascinating, beguiling, bewitching, spellbinding, etc., many of which attempt to describe something that cannot be explained—as does the word charisma, which does come from the same origin as χαρμή.
Words such as these have been used to describe as wide a range of people as Mother Teresa and Greta Garbo; and in the latter case, a critic hit the unseen nail on its elusive head when describing a performance by Garbo’s understudy, who was almost her physical double: ‘She has everything that Garbo has, except whatever it is that Garbo has.’
Greek and Latin may have fewer words for this mysterious quality, but one may name a few of their well-known figures who had it: Themistocles, Sophocles, Pericles, Alcibiades, Socrates, Epicurus, Alexander, Scipio Africanus, Pompey, Sertorius, Julius Caesar, Vespasian—and, of course, Catiline, about whose dark charisma Cicero professes himself to be mystified, in his description during the speech Pro Caelio, 12-14 (recommended).
The dangers of this quality are set out in Shakespeare’s A Lover’s Complaint.