Definition from Wiktionary, the free dictionary
- Rhymes: -ænə
The sense of a persistent optimist comes from the name of the protagonist in a book by Eleanor Porter.
Proper noun 
Pollyanna (plural Pollyannas)
- One who is persistently cheerful and optimistic, even when given cause not to be so.
- You call her an optimist, but I call her an obnoxious Pollyanna.
- (colloquial, US, Southeastern Pennsylvania) A secret Santa gift exchange.