Neither have I, Susan. I believe the expression originated in the blacksmith trade. I checked with master blacksmith Ken Schwarz of Colonial Williamsburg who explained the smith’s point of view. “Iron can be overheated and ‘burned,’ damaged beyond use. If a smith tries to increase productivity, he may put more than one bar into the fire in order to minimize the time waiting for a bar to heat to a working temperature. If the fire is fanned and the iron is not withdrawn before reaching the burning point, the attempt at increased production can actually lead to a reduction in efficiency and material loss. Therefore, too many irons in the fire is counterproductive, causing the smith to work frantically to try to stay ahead of the process.”
The laundry interpretation seems illogical to me. A laundress traditionally used two irons (although Mrs. Pott’s sadirons with detachable handle, below, were sold in sets of three)–one heating on the stove while she ironed with the other. Why have “too many”? You can only use one at a time. For more about irons and ironing, see Myth # 95.