polypyoudaoicibaDictYouDict
polyp: [16] A polyp is etymologically a ‘manyfooted’ creature. The word originally signified ‘octopus’, but in the 18th century was broadened out into a general term for marine invertebrates with tentacles, such as hydras and sea anemones. It comes via French polype and Latin polypus from Greek polúpous ‘cuttlefish’, a compound formed from pólus ‘much, many’ and poús ‘foot’ (source of English pew and podium and related to English foot).

The metaphorical application of the word to a tumour growing from mucous membrane (an allusion to its tentacle-like outgrowths) originated in Greek. Greek pólus (a distant relative of English full and plural) is of course the starting point of many English poly- words, all with the underlying notion of ‘several’ – among them polyglot [17] (etymologically ‘many tongues’), polygon [16], polysyllable [16], and polytechnic [19].

And its plural, polloí ‘many’, is the origin of English hoi polloi [19], literally ‘the many’.
=> foot, full, hoi polloi, pedal, plural, plus, polygon
polyp (n.)youdaoicibaDictYouDict
c. 1400, "nasal tumor," from Middle French polype and directly from Latin polypus "cuttlefish," also "nasal tumor," from Greek (Doric, Aeolic) polypos "octopus, cuttlefish," from polys "many" (see poly-) + pous "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). Etymological sense revived 1742 as a name for hydras and sea anemones (earlier polypus, early 16c.). The Latin word is the source of French poulpe "octopus."
coelenterateyoudaoicibaDictYouDict
"An aquatic invertebrate animal of a phylum that includes jellyfishes, corals, and sea anemones. They typically have a tube- or cup-shaped body with a single opening ringed with tentacles that bear stinging cells (nematocysts)", Late 19th century: from modern Latin Coelenterata, from Greek koilos 'hollow' + enteron 'intestine'.
ActinozoayoudaoicibaDictYouDict
"With plural concord. A class of coelenterates including sea anemones and coral polyps (now more usually called Anthozoa)", Mid 19th cent.; earliest use found in The Penny Cyclopaedia. From scientific Latin Actinozoa ( H.-M. D. de Blainville Man. d'actinologie 186) from actino- + -zoa.
ZoanthariayoudaoicibaDictYouDict
"A group of coelenterates with polyps that bear more than eight tentacles, including the sea anemones and stony corals", Modern Latin (plural), from Greek zōion 'animal' + anthos 'flower'.