Sock

According to the Twelfth Doctor, there was no such thing as socks until there suddenly were. (TV: Under the Lake)

For Christmas, both Susan Campbell and Lucie Miller bought socks for the Eighth Doctor, while the Doctor intended to give Lucie socks as well. The Doctor was very pleased at receiving socks, as they were practical and no-one ever bought him socks. (AUDIO: Relative Dimensions)