The two usages of “descry” — one meaning “to catch sight of” and the other meaning “to find out” — actually come from different etymologies. The former came into Middle English as “descriven” from the Anglo-French “descrire,” meaning “to describe, give an account of,” which came from the Latin “dēscrībere,” meaning “to represent by drawing, describe.” The latter usage came into Middle English as “descrien,” meaning “to announce, make known, reveal, betray,” likely borrowed from the Middle French “descrier,” meaning “to cry, make known.” The separate usages merged in the modern English word “descry” sometime after the 15th century.