excessively particular, critical, or demanding; hard to please: a fastidious eater.
requiring or characterized by excessive care or delicacy; painstaking.
Origin of fastidious
1375–1425;late Middle English < Latinfastīdiōsus squeamish, equivalent to fastīdi(um) lack of appetite, disgust, perhaps by syncope of *fastutīdium (fastu-, combining form of fastus pride, conceit + -tīdium combining form of taediumtedium) + -ōsus-ous
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.