A member of the phylum Echiura, a group of marine worms with a trunk-like proboscis used for feeding.
From Greek 'echis' (viper) + 'oura' (tail), though the 'viper tail' etymology is disputed—some suggest it means 'spiky tail,' referring to the worm's bristly appendages.
Echiurids are 'penis worms' in scientific circles (yes, really!)—their scientific name stuck because of their anatomical resemblance, and they've become a symbol of how sometimes the earliest naming choice, no matter how awkward, becomes permanent in science!
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