Peggy and Peg are short for Margaret. Meggie was a medieval English diminutive form of Margaret (like Maggie), and at some point, for an unknown reason, this changed to Peggy. Its translations in other languages mean daisy (Marguerite in French and Margherita in Italian, for example). Yet in English, we’ve got both the names Daisy and Margaret. Interestingly, the name Margaret originally meant pearl. However, the original Sanskrit word it seems to have been derived from (मञ्जरी or mañjarī) could also mean cluster of blossoms, which is probably why Marguerite in French became the name for the oxeye daisy.

Source: English Language Thoughts