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."