9 Grammatical Pitfalls
c.1300, "silver penny," probably from Middle English sterre (see star (n.)), from the stars that appeared in the design of certain Norman coins, + diminutive suffix -ling. The other theory is that it derives from Old French estedre "stater" (see stater).
Sense broadened by 1560s to "money having the quality of the sterling," and c.1600 to "English money in general." A pound sterling was originally "a pound weight of sterlings," equal to about 240 of them.