"Gimp" of "Gimpy" refers to someone with a limp...It originated, I believe, in the 1920's.....today, of course, it would be politically incorrect to refer to someone by that name...as far as a costume, it could be just regular clothes, & the person would walk, without a cane, with a very noticeable limp......I think it'd be kind of hard to keep that up for an evening of partying!!!!!!!!!!!!!