I thought an interesting origin.
I came upon this sentence from Godwin’s Caleb Williams: “ He observed the particulars of my progress with approbation, and made a favorable report to his master of my industry and genius.”
There was a footnote on the word genius in the notes to the text in the appendix section: ”genius: to the reader unfamiliar with this word’s eighteenth-century usage, it was then understood to denote the peculiar, distinctive, or identifying ‘spirit’ of a person’s character, rather than (as now) suggesting the presence of a virtually transcendent mental superiority.”
From the OED its origin is borrowed from Latin:
Etymology: < classical Latin genius male spirit of a family, existing in the head of the family and subsequently in the divine or spiritual part of each individual, personification of a person’s natural appetites, spirit or personality of an emperor regarded as an object of worship, spirit of a place, spirit of a corporation, (in literature) talent, inspiration, person endowed with talent, also demon or spiritual being in general (2nd cent. a.d.), a formation in -ius (suffix chiefly forming adjectives) on a base ultimately related to that of gignere to beget
I. A supernatural being, and related senses.
a. With reference to classical pagan belief: the tutelary god or attendant spirit allotted to every person at birth to govern his or her fortunes and determine personal character, and finally to conduct him or her out of the world. Also: a guardian spirit similarly associated with a place, institution, thing, etc.; cf. genius loci n. 1. Now chiefly hist.
Worship or propitiation of genii with ceremonies, festivities, dedications, etc., was common throughout the Roman Empire.
Origin: A borrowing from French: Etymon: French génie.
Etymology: < French génie (see genius n.).
In sense 3 ultimately after Arabic jinnī jinnee n. (singular noun corresponding to jinn jinn n.), on account of its phonetic similarity to the French word.
In form genii perhaps influenced by genii, plural of genius n.
Online Etymology Dictionary
1650s, “tutelary spirit,” from French génie, from Latin genius (see genius); used in French translation of “Arabian Nights” to render Arabic jinni, singular of jinn, which it accidentally resembled, and attested in English with this sense from 1748.