BBB Etymology - Geezer

Although used today to mean an old man, "geezer," when it first appeared simply meant a "chap" or "fellow" of any age. "Geezer" began as a dialectical pronunciation of a much older word, "guiser" (as in "disguise"), which appeared in the late 1400's meaning a masquerader or someone who wore a disguise. Both "guiser" and "geezer" were used affectionately to describe someone who was known as a "character" or "odd fellow," and it was only in the 1800's that "geezer" was narrowed to mean an old man.