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mid-15c., "full of pride," from Latin fastidiosus "disdainful, squeamish, exacting," from fastidium "loathing, squeamishness," most likely from *fastu-taidiom, a compound of fastus "contempt, arrogance" and taedium "aversion, disgust." Early use in English was both in passive and active senses. Meaning "squeamish, over-nice" emerged in English 1610s. Related: Fastidiously; fastidiousness.
fastidious fas·tid·i·ous (fā-stĭd'ē-əs, fə-)
Possessing or displaying careful, meticulous attention to detail.
Difficult to please; exacting.
Having complex nutritional requirements. Used of microorganisms.