The word 'sweetish' is a transparent English formation, combining the native adjective 'sweet' with the productive suffix '-ish'. The root 'sweet' originates from the Proto-Germanic swōtuz, itself descended from the Proto-Indo-European root swéh₂dus, meaning 'pleasant, sweet'. The suffix '-ish' has a robust history in English, evolving from the Old English -isc, used to form adjectives of origin or characteristic. The logical construction is straightforward: the core meaning of 'sweet' is softened by the suffix '-ish', which acts as a qualifier, indicating a lesser degree or an approximation of the quality. Thus, the modern word 'sweetish' literally means 'having a slight quality of sweetness', a meaning directly derived from the sum of its recognizable parts.

Structure: sweet (sweet) + ish (having the quality of) sweet: From Old English swēte, meaning 'pleasing to the senses, agreeable'. It functions as the core adjective denoting the taste quality. ish: From Old English -isc, an adjective-forming suffix meaning 'having the qualities of', 'somewhat', or 'approximately'. It functions as a diminutive suffix that modifies the intensity of the root word.