A finger-trace tickle rhyme: circle a fingertip round the baby's palm or tummy for the first two lines, then walk it up with "one step, two step" before the tickle lands. The anticipation is the whole point, and babies learn to wait for it fast.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
Round and round the garden,
Like a teddy bear;
One step, two step,
Tickle you under there!
Traditional rhyme. No printed public-domain source located; wording as commonly recited.