cation (n.)

word-forming element meaning "down, downward," but also "through, on, against, concerning," etc., from Latinized form of Greek kata-, before vowels kat-, from kata "down, downward, down from, down to," from PIE *kmt- "down, with, along" (source also of Hittite kattan (adv.) "below, underneath," katta "along with"). Occasionally in Greek it had senses of "against" (catapult) or "wrongly" (catachresis), also "along, through, over, across, concerning." Also sometimes used as an intensive or with a sense of completion of action (catalogue). Very active in ancient Greek, this prefix is found in English mostly in words borrowed through Latin after c. 1500.

Proto-Indo-European root meaning "to go."

It forms all or part of: Abitur; adit; ambience; ambient; ambit; ambition; ambitious; andante; anion; cation; circuit; coitus; commence; commencement; concomitant; constable; count (n.1) title of nobility; county; dysprosium; errant; exit; initial; initiate; initiation; introit; ion; issue; itinerant; itinerary; janitor; January; Janus; Jena; Mahayana; obiter; obituary; perish; praetor; Praetorian; preterite; sedition; sudden; trance; transient; transit; transitive; viscount.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit e'ti "goes," imas "we go," ayanam "a going, way;" Avestan ae'iti "goes," Old Persian aitiy "goes;" Greek ienai "to go;" Latin ire "to go," iter "a way;" Old Irish ethaim "I go," Irish bothar "a road" (from *bou-itro- "cows' way"), Gaulish eimu "we go;" Lithuanian eiti "to go;" Old Church Slavonic iti "go;" Bulgarian ida "I go;" Russian idti "to go;" Gothic iddja "went."

1834, introduced by English physicist and chemist Michael Faraday (suggested by the Rev. William Whewell, English polymath), coined from Greek ion, neuter present participle of ienai "go," from PIE root *ei- "to go." So called because ions move toward the electrode of opposite charge.