Archaic term for a person who accompanies or attends someone. Not used in modern Japanese; the common modern word is 付き人 (つきびと).
In old documents, there remain records of those who served as attendants to nobles.
Compound of 付き (tsuki, 'attaching') + 者 (mono, 'person'). The exact historical derivation is uncertain, but it follows a common pattern for occupational nouns.