Curious
Middle English: from Old French curios, from Latin curiosus ‘careful’, from cura ‘care’. curious (sense 2) dates from the early 18th century.
wiktionary
From Middle English curious(“careful, meticulous; ingenious, skilful; expert, learned; concerned about (something); eager; curious, inquisitive; prying; carefully or skilfully made; exquisite, fine; sophisticated; recondite; magic or occult; absorbing, painstaking”)[and other forms], [1] from Old French curios, curius (modern French curieux(“curious, inquisitive; interesting, quaint, unusual”)), and its etymonLatin cūriōsus(“careful; complicated, elaborate; careworn; curious, inquisitive; meddlesome, prying”), [2] from cūra(“care, concern; anxiety; sorrow; attention; administration, management; command, office; guardianship”) (from Proto-Indo-European *kʷeys-(“to heed”)) + -ōsus(suffix meaning ‘full of, prone to’ forming adjectives from nouns). The English word is cognate with Italian curioso(“curious, inquisitive”), Occitan curios, Portuguese curioso(“curious, inquisitive; odd, out of the ordinary”), Spanish curioso(“curious, inquisitive; interesting; odd, strange; quaint”). [2]
curi(um) + -ous
etymonline
curious (adj.)
mid-14c., "subtle, sophisticated;" late 14c., "eager to know, inquisitive, desirous of seeing" (often in a bad sense), also "wrought with or requiring care and art;" from Old French curios "solicitous, anxious, inquisitive; odd, strange" (Modern French curieux) and directly from Latin curiosus "careful, diligent; inquiring eagerly, meddlesome," akin to cura "care" (see cure (n.)).
The objective sense of "exciting curiosity" is by 1715 in English. In booksellers' catalogues, the word was a euphemism for "erotic, pornographic" (1877); such material was called curiosa (1883), the Latin neuter plural of curiosus. Related: Curiously; curiousness. Curiouser and curiouser is from "Alice's Adventures in Wonderland" (1865).
Curious and inquisitive may be used in a good or a bad sense, but inquisitive is more often, and prying is only, found in the latter. Curious expresses only the desire to know; inquisitive, the effort to find out by inquiry; prying, the effort to find out secrets by looking and working in improper ways. [Century Dictionary]
