these days, the word "margarita" is the Spanish name for the flower called a daisy in English.
the customary modern Spanish word for "pearl" is "perla". in French it is "perle". in Italian it is "perla".
update: my Italian dictionary does list "margherita" as having "pearl" as a secondary definition, as does one Spanish dictionary (though two others, which i consider better dictionaries, don't).
also, in Latin, it turns out that "margarita" has "pearl" as a primary meaning, not "daisy" (which is not listed in my lexicon as a meaning of Latin "margarita" at all). it comes from the Greek, "margar/ites", which my Greek lexicon also lists as only meaning "pearl" (it is noted as having Persian etymology).
"Prov.: ne mittatis margaritas vestras ante porcos"
— Vulg. Matt. 7, 6.