Anapest (aka, antidactylus) is a short-short-long metrical foot used in poetry (and what Dr. Seuss normally used). This can be remembered as the "plop-plop-fiiiizzz" of an "antacid tablet".
Dactyl (Greek for "finger") is more or less the reverse of anapest, i.e., a long-short-short syllabic meter. This can be remembered by the structure of our own fingers: a long metacarpal followed by two short ones.
(I was mildly tickle to see the latter mnemonic on Wikipedia only after I had thought of it myself. Which makes my insight uniquely commonplace!)