pen and pencil

Montblanc Marc Newson Ballpoint Pen

I would have guessed that "pen" and "pencil" would have the same origin story, but they do not.

PEN goes back to the late 13th century as penne and was a writing implement made from the hard, hollow stem at the base of a feather. In Old French pene was a quill pen or feather which goes back to the Latin penna "a feather, plume." 

You may also know penne as the type of pasta with cylinder-shaped pieces, their ends cut at a bias. Penne is the plural form of the Italian penna (meaning feather but also the writing pen) which also goes back to the Latin penna and is a cognate of the English word pen.

The sense and word was extended to any instrument of similar form used for writing by used a fluid ink. Pen-and-ink as an adjective meaning "made or done with a pen and ink" is attested from 1670s.

Sticks of pure graphite (AKA black lead) were used for marking things in England from the mid-16th century and later in the century the wooden enclosure for the graphite was added to protect the graphite and the hand of the writer.

The word "pencil" came from Old French pincel, from Latin penicillus meaning a "little tail." These early pencils were made as an artist's fine brush of camel hair which could make a fine line and could make letters. They were used art and also for writing before modern lead or chalk pencils. The stylus, a thin metal stick used for scratching in papyrus or wax tablets, was used by the Romans and for palm-leaf manuscripts.

Also during the 16th century, the word pencil was transferred from meaning a type of fine brush to a graphite writing implement. 

In the 19th century, the clay-graphite mix was developed and so was the mass-production. c. Hymen L. Lipman of Philadelphia obtained a patent for the pencil with an attached eraser in 1858. The pencil-sharpener as a mechanical device for putting the point on a lead pencil arrived in 1854.

By extension, the term "pen name" appears in the mid-1800s as being a fictitious name assumed by an author. Earlier, the French nom de plume had been used in English to mean the same thing.

Some other uses that are not in common usage today are "pen-gossip" meaning to gossip by correspondence; a "pencil-pusher" was a derogatory term used to describe a low-level office worker along with "pen-driver" for a clerk. The term "pencil neck" came into use briefly around 1973 to mean a weak person.