The Spanish word 'tarugo' comes from Medieval Latin 'tarus' meaning 'wooden club or peg', which itself derived from Latin 'tarum' meaning 'aloe wood'. The word was formed by combining 'tarus' with the Latin diminutive/pejorative suffix '-ucus'. Over time, the word evolved to mean both a 'wooden peg' in a literal sense, and metaphorically came to refer to a 'dull person' - similar to how English speakers might call someone a 'blockhead'.

While 'tarugo' is a relatively specific term in Spanish, it doesn't have many common related words in modern Spanish. The word stands somewhat alone in Spanish vocabulary, making it a unique term primarily used in carpentry and colloquial insults.

There aren't any common English words directly related to 'tarugo', as the Latin roots 'tarum' and 'tarus' didn't make their way into English vocabulary. However, English speakers might find it helpful to remember that like 'blockhead' or 'wooden-headed', 'tarugo' makes a metaphorical connection between wood and dullness of mind.