'bleary' originates from Middle English, specifically from the verb 'blear' combined with the adjectival suffix '-y' meaning 'characterized by'.

'bleary' changed from Middle English forms such as 'bleer' or 'blear' (verb 'to make dim') and eventually became the modern English adjective 'bleary' by addition of '-y'.

Initially, it meant 'having dim or blurred vision'; over time it has retained that primary sense but has broadened to describe general tiredness or lack of mental clarity ('tired, unfocused').