An Etymological Dictionary of the German Language/jäh

by Friedrich Kluge

jäh, gähe, adj., ‘steep, precipitous, hasty,’ from MidHG. gœhe (also gâch), OHG. gâhi, adj., ‘quick, suddenly, impetuous’; a specifically G. word (with a dial. initial j for g as in jappen; comp. also jähnen with gähnen). From this Fr. gai, ‘gay,’ is borrowed. Its connection. with gehen, gegangen (see Gang), is impossible. Gaudieb is, on the other hand, allied to it.