An Etymological Dictionary of Astronomy and Astrophysics

1. That part of anything that forms or is situated at the top, summit, or upper end.
   

2. The → nucleus and surrounding → coma of a → comet.

Etymology (EN): Head, from O.E. heafod “top of the body,” also “chief person” (cf. O.S. hobid; Goth. haubiþ Ger. Haupt “head”), from PIE *kauput- “head;” cf. Skt. kaput-, kapala- “skull;” L. caput “head;” Pers. dialect Lori: kapu “head,” kapulek “skull, middle of the head;” Kurd. kapol “skull;” Pashto kaparay “skull.”

Etymology (PE): Sar “head,” soru, sorun “horn”
(karnâ “a trumpet-like wind instrument,” variant sornâ “a wind instrument”);
Mid.Pers. sar “head,” sru “horn;” Av. sarah- “head,” srū- “horn, nail;” cf. Skt. śiras- “head, chief;” Gk. kara “head,” karena “head, top,” keras “horn;”
L. cornu “horn,” cerebrum “brain;”
P.Gmc. *khurnaz (Ger. Horn, Du. horen; cognate with E. horn, as above, from PIE *ker- “head, horn;”
O.E. horn “horn of an animal,” also “wind instrument;”
E. horn); PIE base *ker- “head, horn, top, summit.”