Coccyx

[kok-siks] /ˈkɒk sɪks/

noun, plural coccyges
[kok-sahy-jeez, kok-si-jeez] /kɒkˈsaɪ dʒiz, ˈkɒk sɪˌdʒiz/ (Show IPA)
1.
a small triangular bone forming the lower extremity of the spinal column in humans, consisting of four ankylosed rudimentary vertebrae.
2.
a corresponding part in certain animals.
/ˈkɒksɪks/
noun (pl) coccyges (kɒkˈsaɪdʒiːz)
1.
a small triangular bone at the end of the spinal column in man and some apes, representing a vestigial tail
n.

1610s, from Latin coccyx, from Greek kokkyx “cuckoo” (from kokku, like the bird’s English name echoic of its cry), so called by ancient Greek physician Galen because the bone in humans supposedly resembles a cuckoo’s beak.

coccyx coc·cyx (kŏk’sĭks)
n. pl. coc·cy·ges (kŏk-sī’jēz, kŏk’sĭ-jēz’)
The small triangular bone located at the base of the spinal column, formed by the fusion of four rudimentary vertebrae, and articulating above with the sacrum. Also called tailbone.
coccyx
(kŏk’sĭks)
Plural coccyges (kŏk-sī’jēz, kŏk’sĭ-jēz’)
A small triangular bone at the base of the spine in humans and apes. It is composed of several fused vertebrae. Also called tailbone.