Merriam-Webster's Collegiate® Dictionary, 11th Edition
STALE
I. adjective (staler; stalest)
Etymology: Middle English, settled, clear (of ale), not fresh, from Anglo-French estale, probably from Middle Dutch stel old (of beer)
Date: 15th century
tasteless or unpalatable from age , tedious from familiarity , impaired in legal force or effect by reason of being allowed to rest without timely use, action, or demand , impaired in vigor or effectiveness, stalely adverb staleness noun
II. verb (staled; staling)
Date: 1599
transitive verb to make stale, to make common ; cheapen , intransitive verb to become stale,
III. intransitive verb (staled; staling)
Etymology: Middle English; akin to Middle Low German stallen to urinate, stal urine of horses
Date: 15th century
urinate ,
IV. noun
Date: 1548
urine of a domestic animal (as a horse)