English
headmate
From head + -mate.
Formed from head + -mate
Proto-Indo-European *kap- ‘head’
…
Proto-Germanic *haubudą ‘head’
Proto-West Germanic *haubud
Old English hēafod ‘head’
Middle English heed ‘head’
English head
Today it means
noun One of the personalities, identities, or selves in a person with dissociative identity disorder or another form of multiplicity.
Language periods are conventional ranges, not dates for this word.
Etymograph / headmate