All 16 words, sorted alphabetically. Group them into four categories of four.
The four category names, easiest to hardest. No words revealed yet.
Theme name plus one word from each category.
HESITATE, WAFFLE, WAVER, and YO-YO all describe being indecisive or going back and forth without making a firm decision
ANGEL, DEAR, DOLL, and PEACH are all affectionate terms used to describe a lovely, sweet, or kind person
MARBLES, MIND, SENSE, and WITS all relate to lucidity or mental sharpness, as in 'losing your marbles' or 'keeping your wits'
BELL (can't unring a bell), EGG (can't unscramble an egg), GENIE (can't put the genie back in the bottle), and TOOTHPASTE (can't put toothpaste back in the tube) are all parts of metaphors for things that cannot be undone