Pollyanna was a character in a children's book of the same name. She always played the glad game, where she would find something to be optimistic about even in the most negative situations. I think as a name it's quite pretty though it'd be odd to name a girl Pollyanna today, just because it's so old fashioned. The term takes on a more negative meaning though, meaning naively optimistic and moral. The Pollyanna character is sweet, kind-hearted and sympathetic and she teaches others to be optimistic which isn't a bad thing.