Joe, I thought it had to do with the issuing of more shares in the event someone(s) gained control of the shares outstanding in the market place. I didn't think it had to do with one person being a pill or the pill. On the other hand waaaassssss Jerry a pill?
Take a chill pill" must be too recent to be the origin. The Oxford English Dictionary gives "An objectionable person; a bore" as a slang sense of "pill," with the earliest example dated 1897. In a similar sense, "pill" means anything that people don't like to "swallow" or endure. These meanings come from the reluctance with which people swallow medicinal pills. In earlier times, I believe, pills were typically large and often bitter.
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