Systematic

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early 18th century: from French systématique, via late Latin from late Greek sustēmatikos, from sustēma (see system).

wiktionary

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From French systématique, from Ancient Greek συστηματικός(sustēmatikós), from σύστημᾰ(sústēma) +‎ -ῐκός(-ikós). Doublet of systemic.

etymonline

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systematic (adj.)

1670s, "pertaining to a system," from French systématique or directly from Late Latin systematicus, from Greek systematikos "combined in a whole," from systema (genitive systematos); see system. From 1789 as "methodical," often in a bad sense, "ruthlessly methodical." Related: Systematical (1660s); systematically.