rather (adv.)

Old English hraþor "more quickly, earlier, sooner," also "more readily," comparative of hraþe, hræþe "quickly, hastily, promptly, readily, immediately," which is related to hræð "quick, nimble, prompt, ready," from Proto-Germanic *khratha- (source also of Old Norse hraðr, Old High German hrad), from PIE *kret- "to shake." The base form rathe was obsolete by 18c. except in poetry (Tennyson); superlative rathest fell from use by 17c. Meaning "more willingly" is recorded from c. 1300; sense of "more truly" is attested from late 14c.

The rather lambes bene starved with cold

[Spenser, "The Shepheardes Calender" (Februarie), 1579]