the.com/mouthful

means Something hard to say in one go — a word, phrase, or sentence so long or awkward it practically needs chewing — or literally as much food as fits in your mouth at once.

from A straightforward compound of 'mouth' and 'full,' on record since Old/Middle English for the literal sense of a mouth-sized portion of food. The figurative sense — a word or phrase that's a workout to pronounce, or a pointed remark someone 'said a mouthful' — grew naturally from the same image: something so substantial it fills your mouth, whether it's a chunk of bread or a seven-syllable surname.