1A person whose job chiefly involves intellectual work or thinking, as opposed to manual labour; a thinker.
2A worker who manages or is in charge of other workers. In later use chiefly US: (the title or position of) a person who manages a settlement house or other community organization. Now chiefly historical.
Mid 17th century (in an earlier sense). From head + worker, partly after headwork, and partly after handworker.