Also an abbreviation (perhaps) used by pharmacists. (There are the days when I wish that I could do bilingual hard links so that I could remark that in Britain they're called chemists, but ah well...)

It may come from the Latin word recipere meaning ``take, thou'', or it may come from the symbol for Jupiter, or it may have come from the eye of Horus (or udjat), which had an eye with an x below it.