The modern word “pen” comes from the Latin penna, meaning a “feather”. It harks back to the days when scribes wrote using quills.
In the 19th century quills became fitted with replaceable points covered in gold. Later other materials such as tortoiseshell were used. The development of the fountain pen by Waterman in 1884, with its own reservoir of ink, revolutionised pens. Ball point pens came 50 years later and felt tipped pens developed in the 1950’s.
The word “pencil” goes back to the use of a miniature pointed brush, which became known as “a little tail”, penicillum in Latin. The word “tail” in Latin is penis and hence a penicllus was “a little tail”. (This same Latin word gives us penicillin, from the brush-like shape of the Penicillium mold from which it is produced. There may be other applications).
Why a “lead pencil” if the graphite is not lead? In the mid-16th C., a large, extremely pure graphite deposit was found in England, and an economical method was developed for wrapping the graphite in wood and producing the writing instrument (which had already existed for some time). This became the major European source for pencils, and at that time, graphite (from the Greek word graphein, 'to write'), was thought to be a form of lead. It wasn't until the 18th century that graphite was shown to be a form of carbon, but by then "lead pencil" was already in common usage.