tantalizing sample; small taste
A small amount of food offered to whet the appetite or as a polite gesture, often implying it is just a token portion.
It's just a small taste, but please help yourself.
I've prepared some sweets as a little something to go with your tea.
Compound of 口 (mouth) and 汚し (soiling), literally 'mouth-soiling', used humbly to refer to a small offering of food.