means Hopeful and inclined to expect good outcomes, even when the evidence is mixed.

from From Latin 'optimus,' meaning 'best' — the superlative of 'bonus,' good. The word arrived through the 18th-century philosophical doctrine of 'optimism,' the idea (famously championed by Leibniz and mercilessly mocked by Voltaire in Candide) that this is the best of all possible worlds. Over time the heavy philosophy fell away and left the sunnier everyday sense: expecting the best.