I think this is one of those examples of two nations separated by a common language. The American Heritage® Dictionary of the Ehglish Language provides the following:

gee·zer (gē'zər)
n. Slang.
An old person, especially an eccentric old man.

[Probably alteration of dialectal guiser, masquerader, from Middle English gysar, from gysen, to dress, from gyse, guise, fashion. See guise.]

WORD HISTORY   A relationship with a word we know well is disguised in the word geezer. A clue to this relationship is found in British dialect. The English Dialect Dictionary defines geezer as "a queer character, a strangely-acting person," and refers the reader to guiser, "a mummer, masquerader." The citations for guiser refer to practices such as the following: "People, usually children … go about on Christmas Eve, singing, wearing masks, or otherwise disguised," the last word of this passage being the one to which geezer is related.


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The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2003 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


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      - Mark