Etymology
'Vaccine' comes from cow
Edward Jenner used cowpox to protect against smallpox, and Latin vacca, meaning cow, gave the practice its name.
More in Etymology
'Salary' comes from salt
Roman soldiers received an allowance connected to salt, called salarium from the Latin sal. Salt was so valuable it helped preserve armies and empires alike.
'Quarantine' means forty days
Venetian ships waited quaranta giorni, forty days, before docking during plague years. The number became the word for isolation.
'Nightmare' has nothing to do with horses
The mare in nightmare was an Old English demon believed to sit on sleepers' chests. Mare the horse is a separate word entirely.
'Muscle' means little mouse
Latin musculus described the way a flexing bicep ripples like a small mouse moving under the skin.
'Disaster' means bad star
From Italian disastro, it reflects the old belief that misfortune came from unfavourable star alignments.
'Clue' was originally a ball of thread
A clew was the thread Theseus used to escape the labyrinth. The word came to mean anything guiding you to an answer.