late 14c., "thick, sweet liquid," from Old French sirop "sugared drink" (13c.), and perhaps from Italian siroppo, both from Arabic sharab "beverage, wine," literally "something drunk," from verb shariba "he drank" (compare sherbet). Spanish jarabe, jarope, Old Provençal eissarop are from Arabic; Italian sciroppo is via Medieval Latin sirupus. In English, formerly also sirup, sirop.
suffix in pet proper names (such as Johnny, Kitty), first recorded in Scottish c. 1400; according to OED it became frequent in English 15c.-16c. Extension to surnames seems to date from c. 1940. Use with common nouns seems to have begun in Scottish with laddie (1546) and become popular in English due to Burns' poems, but the same formation appears to be represented much earlier in baby and puppy.