From the archives:
Hyoid, from the Greek letter Υ (upsilon) and eidus, Greek for shape; thus, "shaped like an upsilon".
The derivation of the word is better understood if you think of hyoid as "Υoid", The "Υ", however, is not a reference to the shape of the upper case upsilon (Υ) but rather to the lower case form of upsilon (υ).
Upslion, lower and upper cases
Its exclusive anatomical use is for the υ-shaped hyoid bone in the neck and related structures such as the sternohyoid and stylohyoid muscles. It is one of the oldest words in anatomy, first used by the seminal Greek anatomist Herophilus around 300 B.C.
The hyoid bone
If hyoid means Υ-oid, where did the initial "h" come from? In the spoken language of the ancient Greeks, whenever upsilon was used as the first letter in a word, it was always preceded by "rough breathing", i.e., the "h" sound, and was so indicated in Greek writing by a small mark in front of the letter (i.e. 'Υ). Scholars of Greek later replaced the mark with the letter "h". This pattern is seen in many other Greek-derived words, such as those that begin with hyper- and hypo-.
The hyoid is the only bone in the body that does not articulate directly with other bones. It is a favorite of murder-mystery writers because it is evidence of strangulation when broken.