'sappiness' originates from the English word 'sappy', which is derived from the word 'sap', meaning 'juice or fluid of a plant'.

'sappy' changed from the Old English word 'sæp', which referred to the juice or fluid of a plant, and eventually became the modern English word 'sappy', meaning overly sentimental.

Initially, it meant 'full of sap or juice', but over time it evolved into its current meaning of 'overly sentimental'.