UPDATED: The word [manubrium] is Latin and mean "handle", referring to the area where a person holds an instrument or device. To exemplify this, in Spanish the vernacular use of the word [manubrio] refers to the handles of bicycle or even the steering wheel of a car. 

In anatomy, the term is used with the same meaning. In the malleus, a hammer-like ossicle of the middle ear, the manubrium is the handle-like extension of the bone that attaches to the tympanic membrane.

In the case of the sternum, the [manubrium sterni] is the superior portion bound by the sternal angle (of Louis) inferiorly.  The use of the word manubrium can be explained because in early anatomy, the sternum was known by the Latin term [gladius] referring to the similarity of the sternum to the short sword of the gladiators. The area where you hold the sword is the handle, ergo, manubrium.

The manubrium has a superior and median notch called the "suprasternal notch" or the "jugular notch". It is important because in the case of a mediastinoscopy, the incision is made just superior to this landmark. The manubrium articulates superolaterally with the clavicle and inferolaterally with the superior aspect of the cartilage of the second rib. The rest of the rib cartilage articulates with the body of the sternum.

Image property of:CAA.Inc.. Artist: Mark J. Zuptich