Middle English kitthe "people, race, kinsmen, family," also "homeland, native region; kinship, relationship; knowledge, news; propriety, custom," from Old English cyðð "kinship, relationship; kinsfolk, fellow-countrymen, neighbors; native country, home; knowledge, acquaintance, familiarity," from cuð "known," past participle of cunnan "to know" (see can (v.)), from PIE root *gno- "to know."
The alliterative phrase kith and kin (late 14c.) originally meant "country and kinsfolk" and is almost the word's only survival in Modern English. Some cognates have evolved different senses, such as Dutch kunde "skill, competence," German Kunde "knowledge, news, tidings."
*gnō-, Proto-Indo-European root meaning "to know."
It forms all or part of: acknowledge; acquaint; agnostic; anagnorisis; astrognosy; can (v.1) "have power to, be able;" cognition; cognizance; con (n.2) "study;" connoisseur; could; couth; cunning; diagnosis; ennoble; gnome; (n.2) "short, pithy statement of general truth;" gnomic; gnomon; gnosis; gnostic; Gnostic; ignoble; ignorant; ignore; incognito; ken (n.1) "cognizance, intellectual view;" kenning; kith; know; knowledge; narrate; narration; nobility; noble; notice; notify; notion; notorious; physiognomy; prognosis; quaint; recognize; reconnaissance; reconnoiter; uncouth; Zend.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit jna- "know;" Avestan zainti- "knowledge," Old Persian xšnasatiy "he shall know;" Old Church Slavonic znati "recognizes," Russian znat "to know;" Latin gnoscere "get to know," nobilis "known, famous, noble;" Greek gignōskein "to know," gnōtos "known," gnōsis "knowledge, inquiry;" Old Irish gnath "known;" German kennen "to know," Gothic kannjan "to make known."