bonehead n.

Middle English bon, from Old English ban "bone, tusk, hard animal tissue forming the substance of the skeleton; one of the parts which make up the skeleton," from Proto-Germanic *bainan (source also of Old Frisian and Old Saxon ben, Old Norse bein, Danish ben, German Bein). Absent in Gothic, with no cognates outside Germanic (the common PIE root is *ost-); the Norse, Dutch, and German cognates also mean "shank of the leg," and this is the main meaning in Modern German, but English seems never to have had this sense.

To work (one's) fingers to the bone is from 1809. To have a bone to pick (1560s) is an image of a dog struggling to crack or gnaw a bone (to pick a bone "strip a bone by picking or gnawing" is attested from late 15c.); to be a bone of contention (1560s) is of two dogs fighting over a bone; the images seem to have become somewhat merged. Also compare bones.

Bone-china, which is mixed with bone-dust, is so called by 1854. Bone-shaker (1874) was an old name for the early type of bicycle, before rubber tires.

Old English heafod "top of the body," also "upper end of a slope," also "chief person, leader, ruler; capital city," from Proto-Germanic *haubid (source also of Old Saxon hobid, Old Norse hofuð, Old Frisian haved, Middle Dutch hovet, Dutch hoofd, Old High German houbit, German Haupt, Gothic haubiþ "head"), from PIE root *kaput- "head."

Modern spelling is early 15c., representing what was then a long vowel (as in heat) and remained after pronunciation shifted. Of rounded tops of plants from late 14c. Meaning "origin of a river" is mid-14c. Meaning "obverse of a coin" (the side with the portrait) is from 1680s; meaning "foam on a mug of beer" is first attested 1540s; meaning "toilet" is from 1748, based on location of crew toilet in the bow (or head) of a ship.

Synechdochic use for "person" (as in head count) is first attested late 13c.; of cattle, etc., in this sense from 1510s. As a height measure of persons, from c. 1300. Meaning "drug addict" (usually in a compound with the preferred drug as the first element) is from 1911.

To be over (one's) head "beyond one's comprehension" is by 1620s. To give head "perform fellatio" is from 1950s. Phrase heads will roll "people will be punished" (1930) translates Adolf Hitler. Head case "eccentric or insane person" is from 1966. Head game "mental manipulation" attested by 1972.